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This panel provides information on past usage of this interatomic potential (IP) powered by the OpenKIM Deep Citation framework. The word cloud indicates typical applications of the potential. The bar chart shows citations per year of this IP (bars are divided into articles that used the IP (green) and those that did not (blue)). The complete list of articles that cited this IP is provided below along with the Deep Citation determination on usage. See the Deep Citation documentation for more information.
363 Citations (221 used)
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USED (high confidence) L. Wei, C. Zhang, Q.-Y. Zheng, Z. Zeng, and Y. Li, “Individual cascade annealing in BCC tungsten: effects of size and spatial distributions of defects,” RSC Advances. 2022. link Times cited: 2 Abstract: To investigate effects of size and spatial distributions of … read moreAbstract: To investigate effects of size and spatial distributions of defects from primary damage to annealing of an individual cascade, molecular dynamics (MD) and object kinetic Monte Carlo (OKMC) are applied for simulating cascade generation and annealing. MD cascade simulations of tungsten are carried out with two typical embedded atom method potentials for cascade energies in the range from 0.1 to 100 keV at 300 K. The simulation results show that even though the number of survival defects varies slightly, these two potentials produce very different interstitial cluster (IC) size distribution and defect spatial distribution with cascade energies larger than 30 keV. Furthermore, OKMC is used to model individual cascade annealing. It demonstrates that larger-sized ICs and closely distributed SIAs in the cascade region will induce a much higher recombination fraction for individual cascade annealing. Therefore, special attention should be paid to the size and spatial distributions of defects for primary damage in the multi-scale simulation framework. read less USED (high confidence) S. Sassi et al., “Energy loss in low energy nuclear recoils in dark matter detector materials,” Physical Review D. 2022. link Times cited: 5 Abstract: Recent progress in phonon-mediated detectors with eV-scale n… read moreAbstract: Recent progress in phonon-mediated detectors with eV-scale nuclear recoil energy sensitivity requires an understanding of the effect of the crystalline defects on the energy spectrum expected from dark matter or neutrino coherent scattering. We have performed molecular dynamics simulations to determine the amount of energy stored in the lattice defects as a function of the recoil direction and energy. This energy can not be observed in the phonon measurement, thus affecting the observed energy spectrum compared to the underlying true recoil energy spectrum. We describe this effect for multiple commonly used detector materials and demonstrate how the predicted energy spectrum from dark matter scattering is modified. read less USED (high confidence) U. Bhardwaj, A. Sand, and M. Warrier, “Graph theory based approach to characterize self interstitial defect morphology,” Computational Materials Science. 2021. link Times cited: 9 USED (high confidence) Z.-Z. Li et al., “Strain Dependence of Energetics and Kinetics of Vacancy in Tungsten,” Materials. 2020. link Times cited: 9 Abstract: We investigate the influence of hydrostatic/biaxial strain o… read moreAbstract: We investigate the influence of hydrostatic/biaxial strain on the formation, migration, and clustering of vacancy in tungsten (W) using a first-principles method, and show that the vacancy behaviors are strongly dependent on the strain. Both a monovacancy formation energy and a divacancy binding energy decrease with the increasing of compressive hydrostatic/biaxial strain, but increase with the increasing of tensile strain. Specifically, the binding energy of divacancy changes from negative to positive when the hydrostatic (biaxial) tensile strain is larger than 1.5% (2%). These results indicate that the compressive strain will facilitate the formation of monovacancy in W, while the tensile strain will enhance the attraction between vacancies. This can be attributed to the redistribution of electronic states of W atoms surrounding vacancy. Furthermore, although the migration energy of the monovacancy also exhibits a monotonic linear dependence on the hydrostatic strain, it shows a parabola with an opening down under the biaxial strain. Namely, the vacancy mobility will always be promoted by biaxial strain in W, almost independent of the sign of strain. Such unexpected anisotropic strain-enhanced vacancy mobility originates from the Poisson effect. On the basis of the first-principles results, the nucleation of vacancy clusters in strained W is further determined with the object kinetic Monte Carlo simulations. It is found that the formation time of tri-vacancy decrease significantly with the increasing of tensile strain, while the vacancy clusters are not observed in compressively strained W, indicating that the tensile strain can enhance the formation of voids. Our results provide a good reference for understanding the vacancy behaviors in W. read less USED (high confidence) U. Bhardwaj, A. Sand, and M. Warrier, “Classification of clusters in collision cascades,” Computational Materials Science. 2020. link Times cited: 11 USED (high confidence) S. Das, H. Yu, K. Mizohata, E. Tarleton, and F. Hofmann, “Modified deformation behaviour of self-ion irradiated tungsten: A combined nano-indentation, HR-EBSD and crystal plasticity study,” International Journal of Plasticity. 2019. link Times cited: 27 USED (high confidence) F. J. Dom’inguez-Guti’errez et al., “On the classification and quantification of crystal defects after energetic bombardment by machine learned molecular dynamics simulations,” Nuclear Materials and Energy. 2019. link Times cited: 10 USED (high confidence) D. R. Mason, A. Sand, and S. Dudarev, “Atomistic-object kinetic Monte Carlo simulations of irradiation damage in tungsten,” Modelling and Simulation in Materials Science and Engineering. 2019. link Times cited: 13 Abstract: We describe the development of a new object kinetic Monte Ca… read moreAbstract: We describe the development of a new object kinetic Monte Carlo (kMC) code where the elementary defect objects are off-lattice atomistic configurations. Atomic-level transitions are used to transform and translate objects, to split objects and to merge them together. This gradually constructs a database of atomic configurations- a set of relevant defect objects and their possible events generated on-the-fly. Elastic interactions are handled within objects with empirical potentials at short distances, and between spatially distinct objects using the dipole tensor formalism. The model is shown to evolve mobile interstitial clusters in tungsten faster than an equivalent molecular dynamics (MD) simulation, even at elevated temperatures. We apply the model to the evolution of complex defects generated using MD simulations of primary radiation damage in tungsten. We show that we can evolve defect structures formed in cascade simulations to experimentally observable timescales of seconds while retaining atomistic detail. We conclude that the first few nanoseconds of simulation following cascade initiation would be better performed using MD, as this will capture some of the near-temperature-independent evolution of small highly-mobile interstitial clusters. For the 20keV cascade annealing simulations considered here, we observe internal relaxations of sessile objects. These relaxations would be difficult to capture using conventional object kMC, yet are important as they establish the conditions for long timescale evolution. read less USED (high confidence) J. Wang, B. He, W.-H. Song, and W. Dang, “Energetics, kinetics and dynamics of self-interstitial clusters in bcc tungsten,” Molecular Simulation. 2019. link Times cited: 8 Abstract: ABSTRACT The configuration, slipping and rotation of self-in… read moreAbstract: ABSTRACT The configuration, slipping and rotation of self-interstitial atoms cluster along <111> crystal orientation with different sizes in a tungsten are investigated systematically with molecular dynamics. It is found that (I) the SIA clusters with high symmetry are always favoured; (II) the SIA clusters can undergo one-dimensional fast migration along <111> direction, and their migration barriers are no more than 0.07 eV, which is expected due to the strong interaction in the SIA clusters; (III) the rotation energy barriers of the SIA clusters are rather high and they are basically positively correlated with the size of the cluster. For example, the reorientation barrier is 0.66 eV for 1 SIA, 1.2–1.8 eV for SIAn (2 ≤ n ≤ 5) clusters and over 2.7 eV for SIAn (6 ≤ n ≤ 7) clusters. Compared with slipping of SIA clusters, is an infrequent event, especially for larger SIAs cluster, the vast majority SIAs cluster would have already recombination with vacancies or annihilates at surface and grain boundary through slipping before rotation, which explained that there are very low density of SIAs cluster found in the experiment. read less USED (high confidence) S. Dudarev, D. Mason, E. Tarleton, P. Ma, and A. Sand, “A multi-scale model for stresses, strains and swelling of reactor components under irradiation,” Nuclear Fusion. 2018. link Times cited: 61 Abstract: Predicting strains, stresses and swelling in nuclear power p… read moreAbstract: Predicting strains, stresses and swelling in nuclear power plant components exposed to irradiation directly from the observed or computed defect and dislocation microstructure is a fundamental problem of fusion power plant design that has so far eluded a practical solution. We develop a model, free from parameters not accessible to direct evaluation or observation, that is able to provide estimates for irradiation-induced stresses and strains on a macroscopic scale, using information about the distribution of radiation defects produced by high-energy neutrons in the microstructure of materials. The model exploits the fact that elasticity equations involve no characteristic spatial scale, and hence admit a mathematical treatment that is an extension to that developed for the evaluation of elastic fields of defects on the nanoscale. In the analysis given below we use, as input, the radiation defect structure data derived from ab initio density functional calculations and large-scale molecular dynamics simulations of high-energy collision cascades. We show that strains, stresses and swelling can be evaluated using either integral equations, where the source function is given by the density of relaxation volumes of defects, or they can be computed from heterogeneous partial differential equations for the components of the stress tensor, where the density of body forces is proportional to the gradient of the density of relaxation volumes of defects. We perform a case study where strains and stresses are evaluated analytically and exactly, and develop a general finite element method implementation of the method, applicable to a broad range of predictive simulations of strains and stresses induced by irradiation in materials and components of any geometry in fission or fusion nuclear power plants. read less USED (high confidence) D. Mason, D. Nguyen-Manh, and C. Becquart, “An empirical potential for simulating vacancy clusters in tungsten,” Journal of Physics: Condensed Matter. 2017. link Times cited: 50 Abstract: We present an empirical interatomic potential for tungsten, … read moreAbstract: We present an empirical interatomic potential for tungsten, particularly well suited for simulations of vacancy-type defects. We compare energies and structures of vacancy clusters generated with the empirical potential with an extensive new database of values computed using density functional theory, and show that the new potential predicts low-energy defect structures and formation energies with high accuracy. A significant difference to other popular embedded-atom empirical potentials for tungsten is the correct prediction of surface energies. Interstitial properties and short-range pairwise behaviour remain similar to the Ackford-Thetford potential on which it is based, making this potential well-suited to simulations of microstructural evolution following irradiation damage cascades. Using atomistic kinetic Monte Carlo simulations, we predict vacancy cluster dissociation in the range 1100–1300 K, the temperature range generally associated with stage IV recovery. read less USED (high confidence) X.-yan Li et al., “Annihilating vacancies via dynamic reflection and emission of interstitials in nano-crystal tungsten,” Nuclear Fusion. 2017. link Times cited: 15 Abstract: Radiation damage not only seriously degrades the mechanical … read moreAbstract: Radiation damage not only seriously degrades the mechanical properties of tungsten (W) but also enhances hydrogen retention in the material. Introducing a large amount of defect sinks, e.g. grain boundaries (GBs) is an effective method for improving radiation-resistance of W. However, the mechanism by which the vacancies are dynamically annihilated at long timescale in nano-crystal W is still not clear. The dynamic picture for eliminating vacancies with single interstitials and small interstitial-clusters has been investigated by combining molecular dynamics, molecular statics and object Kinetic Monte Carlo methods. On one hand, the annihilation of bulk vacancies was enhanced due to the reflection of an interstitial-cluster of parallel 〈111〉 crowdions by the GB. The interstitial-cluster was observed to be reflected back into the grain interior when approaching a locally dense GB region. Near this region, the energy landscape for the interstitial was featured by a shoulder, different to the decreasing energy landscape of the interstitial near a locally loose region as indicative of the sink role of the GB. The bulk vacancy on the reflection path was annihilated. On the other hand, the dynamic interstitial emission efficiently anneals bulk vacancies. The single interstitial trapped at the GB firstly moved along the GB quickly and clustered to be the di-interstitial therein, reducing its mobility to a value comparable to that that for bulk vacancy diffusion. Then, the bulk vacancy was recombined via the coupled motion of the di-interstitial along the GB, the diffusion of the vacancy towards the GB and the accompanying interstitial emission. These results suggest that GBs play an efficient role in improving radiation-tolerance of nano-crystal W via reflecting highly-mobile interstitials and interstitial-clusters into the bulk and annihilating bulk vacancies, and via complex coupling of in-boundary interstitial diffusion, clustering of the interstitial and vacancy diffusion in the bulk. read less USED (high confidence) R. Harrison, G. Greaves, J. Hinks, and S. Donnelly, “Engineering self-organising helium bubble lattices in tungsten,” Scientific Reports. 2017. link Times cited: 35 USED (high confidence) D. Dragoni, T. Daff, G. Csányi, and N. Marzari, “Achieving DFT accuracy with a machine-learning interatomic potential: thermomechanics and defects in bcc ferromagnetic iron,” arXiv: Materials Science. 2017. link Times cited: 167 Abstract: We show that the Gaussian Approximation Potential machine le… read moreAbstract: We show that the Gaussian Approximation Potential machine learning framework can describe complex magnetic potential energy surfaces, taking ferromagnetic iron as a paradigmatic challenging case. The training database includes total energies, forces, and stresses obtained from density-functional theory in the generalized-gradient approximation, and comprises approximately 150,000 local atomic environments, ranging from pristine and defected bulk configurations to surfaces and generalized stacking faults with different crystallographic orientations. We find the structural, vibrational and thermodynamic properties of the GAP model to be in excellent agreement with those obtained directly from first-principles electronic-structure calculations. There is good transferability to quantities, such as Peierls energy barriers, which are determined to a large extent by atomic configurations that were not part of the training set. We observe the benefit and the need of using highly converged electronic-structure calculations to sample a target potential energy surface. The end result is a systematically improvable potential that can achieve the same accuracy of density-functional theory calculations, but at a fraction of the computational cost. read less USED (high confidence) Y.-S. Lin, M. Mrovec, and V. Vitek, “Importance of inclusion of the effect of s electrons into bond-order potentials for transition bcc metals with d-band mediated bonding,” Modelling and Simulation in Materials Science and Engineering. 2016. link Times cited: 5 Abstract: In bond-order potentials (BOPs) for transition metals only t… read moreAbstract: In bond-order potentials (BOPs) for transition metals only the bonding mediated by the d electrons is included explicitly and the covalent part of the cohesive energy is evaluated using Slater–Koster dd bond integrals. However, the effect of s electrons with orbitals centered on atoms neighboring the corresponding dd bond is not necessarily negligible. As shown in Nguyen-Manh et al (2000 Phys. Rev. Lett. 85 4136) this can be taken into account via screening of the dd bond integrals. In a recent paper (Lin et al 2014 Model. Simul. Mater. Sci. Eng. 22 034002) the dd bond integrals were determined using a projection scheme utilizing atomic orbitals that give the best representation of the electronic wave functions in the calculations based on the density functional theory (DFT) (Madsen et al 2011 Phys. Rev. B 83 4119) and it was inferred that in this case the effect of s electrons was already included. In this paper we analyze this hypothesis by comparing studies employing BOPs with both unscreened and screened dd bond integrals. In all cases results are compared with calculations based on DFT and/or experiments. Studies of structures alternate to the bcc lattice, transformation paths that connect the bcc structure with fcc, simple cubic (sc), body centered tetragonal (bct) and hcp structures via continuously distorted configurations and calculations of γ-surfaces were all found to be insensitive to the screening of bond integrals. On the other hand, when the bond integrals are screened, formation energies of vacancies are improved and calculated phonon dispersion spectra reproduce the experimentally observed ones much better. Most importantly, dislocation core structure and dislocation glide are significantly different without and with screening of dd bond integrals. The latter lead to a much better agreement with available experiments. These findings suggest that the effect of s electrons on dd bonds, emulated by the screening of corresponding bond integrals, is the least significant when the lattice is distorted away from the ideal bcc structure homogeneously even if such distortion is large. On the other hand, when the distortion is local and inhomogeneous the impact of screening of the dd bond integrals is significant. In the studies presented in this paper such local inhomogeneities occur when phonons propagate through the lattice, at point defects and in the cores of dislocations. read less USED (high confidence) A. Sand, M. J. Aliaga, M. Caturla, and K. Nordlund, “Surface effects and statistical laws of defects in primary radiation damage: Tungsten vs. iron,” Europhysics Letters. 2016. link Times cited: 48 Abstract: We have investigated the effect of surfaces on the statistic… read moreAbstract: We have investigated the effect of surfaces on the statistics of primary radiation damage, comparing defect production in the bcc metals iron (Fe) and tungsten (W). Through molecular dynamics simulations of collision cascades we show that vacancy as well as interstitial cluster sizes follow scaling laws in both bulk and thin foils in these materials. The slope of the vacancy cluster size distribution in Fe is clearly affected by the surface in thin foil irradiation, while in W mainly the overall frequency is affected. Furthermore, the slopes of the power law distributions in bulk Fe are markedly different from those in W. The distinct behaviour of the statistical distributions uncovers different defect production mechanisms effective in the two materials, and provides insight into the underlying reasons for the differing behaviour observed in TEM experiments of low-dose ion irradiation in these metals. read less USED (high confidence) J.-F. Hu, L.-peng Feng, W. Zhang, Y. Li, and Y. Lu, “Detection of DNA Bases Using Fe Atoms and Graphene,” Chinese Physics Letters. 2016. link Times cited: 1 Abstract: The adsorption of DNA bases on a magnetic probe composed of … read moreAbstract: The adsorption of DNA bases on a magnetic probe composed of Fe atoms and graphene is studied by using first-principles calculations. The stability of geometry, the electronic structure and magnetic property are investigated. The results indicate that four DNA bases, i.e., adenine, thymine, cytosine and guanine, can all be adsorbed on the probe solidly. However, the magnetic moments of the composite structure can be observed only when adenine adsorbs on the probe. In the cases of the adsorption of the other three bases, the magnetic moments of the composite structure are zero. Based on the significant change of magnetic moment of the composite structure, adenine can be distinguished conveniently from thymine, cytosine and guanine. This work may provide a new way to detect DNA bases. read less USED (high confidence) M. Li, J. Wang, B. Fu, and Q. Hou, “A molecular dynamics study of melting and dissociation of tungsten nanoparticles,” AIP Advances. 2015. link Times cited: 16 Abstract: Molecular dynamics simulations were conducted to study the m… read moreAbstract: Molecular dynamics simulations were conducted to study the melting and dissociation of free tungsten nanoparticles. For the various interatomic potentials applied, the melting points of the tungsten nanoparticles increased with increasing nanoparticle diameter. Combining these results with the melting point of bulk tungsten in the experiment, the melting point of nanoparticles with diameters ranging from 4 to 12 nm could be determined. As the temperature increases, free nanoparticles are subject to dissociation phenomena. The dissociation rate was observed to follow Arrhenius behavior, and the Meyer–Neldel rule was obeyed. These results are useful in understanding the behavior of tungsten dust generated in nuclear fusion devices as well as for the preparation, formation, and application of tungsten powders. read less USED (high confidence) X. Li, Y. Liu, Y. Yu, G. Niu, G. Luo, and X. Shu, “Molecular Statics Simulation of Hydrogen Defect Interaction in Tungsten,” Plasma Science & Technology. 2015. link Times cited: 4 Abstract: Hydrogen (H) defect interactions have been investigated by m… read moreAbstract: Hydrogen (H) defect interactions have been investigated by molecular statics simulations in tungsten (W), including H-H interactions and interactions between H and W self-interstitial atoms. The interactions between H and small H-vacancy clusters are also demonstrated; the binding energies of an H, a vacancy and a self-interstitial W to an H-vacancy cluster depend on the H-to-vacancy ratio. We conclude that H bubble formation needs a high concentration of H in W for the H bubble nucleation and growth, which are also governed by the H-to-vacancy ratio of the cluster. The vacancy first combines with H atoms and a cluster forms, then the H-vacancy cluster goes through the whole process of vacancy capture, H capture, and vacancy capture again, and as a result the H-vacancy cluster grows larger and larger. Finally, the H bubble forms. read less USED (high confidence) X. Yi et al., “Direct observation of size scaling and elastic interaction between nano-scale defects in collision cascades,” Europhysics Letters. 2015. link Times cited: 113 Abstract: Using in situ transmission electron microscopy, we have dire… read moreAbstract: Using in situ transmission electron microscopy, we have directly observed nano-scale defects formed in ultra-high–purity tungsten by low-dose high-energy self-ion irradiation at 30 K. At cryogenic temperature lattice defects have reduced mobility, so these microscope observations offer a window on the initial, primary damage caused by individual collision cascade events. Electron microscope images provide direct evidence for a power-law size distribution of nano-scale defects formed in high-energy cascades, with an upper size limit independent of the incident ion energy, as predicted by Sand et al. (EPL, 103 (2013) 46003). Furthermore, the analysis of pair distribution functions of defects observed in the micrographs shows significant intra-cascade spatial correlations consistent with strong elastic interaction between the defects. read less USED (high confidence) C. G. Zhang, W. Zhou, Y. Li, Z. Zeng, and X. Ju, “Primary radiation damage near grain boundary in bcc tungsten by molecular dynamics simulations,” Journal of Nuclear Materials. 2015. link Times cited: 42 USED (high confidence) G. Nandipati, W. Setyawan, H. Heinisch, K. Roche, R. Kurtz, and B. Wirth, “Displacement cascades and defect annealing in tungsten, Part II: Object kinetic Monte Carlo Simulation of Tungsten Cascade Aging,” Journal of Nuclear Materials. 2014. link Times cited: 30 USED (high confidence) M. Li, J. Cui, J. Wang, and Q. Hou, “Molecular dynamics simulations of cumulative helium bombardments on tungsten surfaces,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2013. link Times cited: 26 USED (high confidence) B. Tyburska-Püschel and V. Alimov, “On the reduction of deuterium retention in damaged Re-doped W,” Nuclear Fusion. 2013. link Times cited: 35 Abstract: Modelling tritium retention in radiation-damaged pure-tungst… read moreAbstract: Modelling tritium retention in radiation-damaged pure-tungsten samples, the concentration of deuterium retained in the tungsten-ion-induced damage zone decreases with increasing exposure temperature; whereas for a similarly treated tungsten–rhenium alloy, it can drop significantly faster than in pure tungsten, given sufficiently high temperatures. In contrast, similar changes in retention behaviour were not observed in undamaged samples. Based on these findings, as well as on corresponding previous TEM results, it is concluded that the concentration of high-energy radiation-induced defects responsible for trapping of deuterium is lower in the alloy than in pure tungsten. Therefore, a small amount of transmutation rhenium in damaged tungsten should be able to keep tritium retention to a low level in ITER. read less USED (high confidence) A. Sand, S. Dudarev, and K. Nordlund, “High-energy collision cascades in tungsten: Dislocation loops structure and clustering scaling laws,” Europhysics Letters. 2013. link Times cited: 189 Abstract: Recent experiments on in situ high-energy self-ion irradiati… read moreAbstract: Recent experiments on in situ high-energy self-ion irradiation of tungsten (W) show the occurrence of unusual cascade damage effects resulting from single-ion impacts, shedding light on the nature of radiation damage expected in the tungsten components of a fusion reactor. In this paper, we investigate the dynamics of defect production in 150 keV collision cascades in W at atomic resolution, using molecular-dynamics simulations and comparing predictions with experimental observations. We show that cascades in W exhibit no subcascade break-up even at high energies, producing a massive, unbroken molten area, which facilitates the formation of large defect clusters. Simulations show evidence of the formation of both and interstitial-type dislocation loops, as well as the occurrence of cascade collapse resulting in vacancy-type dislocation loops, in excellent agreement with experimental observations. The fractal nature of the cascades gives rise to a scale-less power-law–type size distribution of defect clusters. read less USED (high confidence) W. Zhou, Y. Li, L.-F. Huang, Z. Zeng, and X. Ju, “Dynamical Behaviors of Self-interstitial Atoms in Tungsten,” Journal of Nuclear Materials. 2013. link Times cited: 19 USED (high confidence) S. Dudarev et al., “Langevin model for real-time Brownian dynamics of interacting nanodefects in irradiated metals,” Physical Review B. 2010. link Times cited: 61 Abstract: In situ real-time electron microscope observations of metals… read moreAbstract: In situ real-time electron microscope observations of metals irradiated with ultrahigh-energy electrons or energetic ions show that the dynamics of microstructural evolution in these materials is strongly influenced by long-range elastic interactions between mobile nanoscale radiation defects. Treating long-range interactions is also necessary for modeling microstructures formed in ex situ high-dose-rate ion-beam irradiation experiments, and for interpolating the ion-beam irradiation data to the low-dose-rate limit characterizing the neutron irradiation environments of fission or fusion power plants. We show that simulations, performed using an algorithm where nanoscale radiation defects are treated as interacting Langevin particles, are able to match and explain the real-time dynamics of nanodefects observed in in situ electron microscope experiments. read less USED (high confidence) I. Valikova and A. Nazarov, “Simulation of characteristics determining pressure effects on self-diffusion in BCC and FCC metals,” The Physics of Metals and Metallography. 2010. link Times cited: 14 USED (high confidence) N. Itoh, D. M. Duffy, D. M. Duffy, S. Khakshouri, and A. Stoneham, “Making tracks: electronic excitation roles in forming swift heavy ion tracks,” Journal of Physics: Condensed Matter. 2009. link Times cited: 206 Abstract: Swift heavy ions cause material modification along their tra… read moreAbstract: Swift heavy ions cause material modification along their tracks, changes primarily due to their very dense electronic excitation. The available data for threshold stopping powers indicate two main classes of materials. Group I, with threshold stopping powers above about 10 keV nm−1, includes some metals, crystalline semiconductors and a few insulators. Group II, with lower thresholds, comprises many insulators, amorphous materials and high Tc oxide superconductors. We show that the systematic differences in behaviour result from different coupling of the dense excited electrons, holes and excitons to atomic (ionic) motions, and the consequent lattice relaxation. The coupling strength of excitons and charge carriers with the lattice is crucial. For group II, the mechanism appears to be the self-trapped exciton model of Itoh and Stoneham (1998 Nucl. Instrum. Methods Phys. Res. B 146 362): the local structural changes occur roughly when the exciton concentration exceeds the number of lattice sites. In materials of group I, excitons are not self-trapped and structural change requires excitation of a substantial fraction of bonding electrons, which induces spontaneous lattice expansion within a few hundred femtoseconds, as recently observed by laser-induced time-resolved x-ray diffraction of semiconductors. Our analysis addresses a number of experimental results, such as track morphology, the efficiency of track registration and the ratios of the threshold stopping power of various materials. read less USED (high confidence) A. P. Shpak, S. Kotrechko, T. Mazilova, and I. Mikhailovskij, “Inherent tensile strength of molybdenum nanocrystals,” Science and Technology of Advanced Materials. 2009. link Times cited: 24 Abstract: The strength of Mo nanorods was measured under uniaxial tens… read moreAbstract: The strength of Mo nanorods was measured under uniaxial tension. Tensile tests of 〈 110〉-oriented single-crystalline molybdenum rod-shaped specimens with diameters from 25 to 90 nm at the apex were conducted inside a field-ion microscope (FIM). The nanocrystals were free from dislocations, planar defects and microcracks, and exhibited the plastic mode of failure under uniaxial tension with the formation of a chisel-edge tip by multiple gliding in the and deformation systems. The experimental values of tensile strength vary between 6.3 and 19.8 GPa and show a decrease with increasing nanorod diameter. A molecular dynamic simulation of Mo nanorod tension also suggests that the strength decreases from 28.8 to 21.0 GPa when the rod diameter increases from 3.1 to 15.7 nm. The maximum values of experimental strength are thought to correspond to the inherent strength of Mo nanocrystals under uniaxial tension (19.8 GPa, or 7.5% of Young's modulus). read less USED (high confidence) S. Fitzgerald and D. Nguyen-Manh, “Peierls potential for crowdions in the bcc transition metals.,” Physical review letters. 2008. link Times cited: 46 Abstract: We present the first derivation of the analytic expression f… read moreAbstract: We present the first derivation of the analytic expression for the Peierls-Nabarro potential for crowdion migration using the double sine-Gordon model. The analysis is guided by the group-specific trend in the shapes of the periodic lattice potentials calculated for the body-centered-cubic transition metals in groups 5B and 6B of the periodic table. We combine density-functional calculations of the crowdion's profile and environment with an extended version of the analytical Frenkel-Kontorova model, and determine the effective potential experienced by the defect's center of mass. This reveals important underlying differences between the metals in these groups, which are inaccessible to either the numerical or analytical approaches alone, and accounts for the previously unexplained significantly higher crowdion migration temperatures observed in the metals of group 6B relative to those of group 5B. read less USED (high confidence) M. R. Gilbert, S. Dudarev, P. Derlet, and D. Pettifor, “Structure and metastability of mesoscopic vacancy and interstitial loop defects in iron and tungsten,” Journal of Physics: Condensed Matter. 2008. link Times cited: 89 Abstract: The most recent observations of dynamical time-dependent flu… read moreAbstract: The most recent observations of dynamical time-dependent fluctuating behaviour of mesoscopic radiation defects in body-centred cubic metals (Arakawa et al 2006 Phys. Rev. Lett. 96 125506; 2007 Science 318 956–9; Yao et al 2008 Phil. Mag. at press) have highlighted the need to develop adequate quantitative models for the structural stability of defects in the mesoscopic limit where defects are accessible to direct in situ electron microscope imaging. In pursuit of this objective, we investigate and compare several types of mesoscopic vacancy and interstitial defects in iron and tungsten by simulating them using recently developed many-body interatomic potentials. We show that the mesoscopic vacancy dislocation loops observed in ion-irradiated materials are, without exception, metastable with respect to the transformation into spherical voids, but that the rate of this transformation and even the specific type of the transformation mechanism depend on the defect size and the properties of the material. read less USED (high confidence) Z. Lin, R. A. Johnson, and L. Zhigilei, “Computational study of the generation of crystal defects in a bcc metal target irradiated by short laser pulses,” Physical Review B. 2008. link Times cited: 93 Abstract: The generation of crystal defects in a Cr target irradiated … read moreAbstract: The generation of crystal defects in a Cr target irradiated by a short, 200 fs, laser pulse is investigated in computer simulations performed with a computational model that combines the classical molecular dynamics method with a continuum description of the laser excitation of conduction band electrons, electron-phonon coupling, and electron heat conduction. Interatomic interactions are described by the embedded atom method EAM potential with a parametrization designed for Cr. The potential is tested by comparing the properties of the EAM Cr material with experimental data and predictions of density functional theory calculations. The simulations are performed at laser fluences close to the threshold for surface melting. Fast temperature variation and strong thermoelastic stresses produced by the laser pulse are causing surface melting and epitaxial resolidification, transient appearance of a high density of stacking faults along the 110 planes, and generation of a large number of point defects vacancies and self-interstitials. The stacking faults appear as a result of internal shifts in the crystal undergoing a rapid uniaxial expansion in the direction normal to the irradiated surface. The stacking faults are unstable and disappear shortly after the laser-induced tensile stress wave leaves the surface region of the target. Thermally activated generation of vacancy-interstitial pairs during the initial temperature spike and quick escape of highly mobile self-interstitials to the melting front or the free surface of the target, along with the formation of vacancies at the solid-liquid interface during the fast resolidification process, result in a high density of vacancies, on the order of 10 3 per lattice site, created in the surface region of the target. The strong supersaturation of vacancies can be related to the incubation effect in multipulse laser ablation/damage and should play an important role in mixing/alloying of multicomponent or composite targets. read less USED (low confidence) A. I. Kochaev and P. L’vov, “Anisotropic diffusion in symmetric tilt grain boundaries in bcc iron: A DFT study,” Materialia. 2023. link Times cited: 0 USED (low confidence) B. Sharma, Y. S. Teh, B. Sadigh, S. Hamel, V. Bulatov, and A. Samanta, “Development of an interatomic potential for the W–Ta system,” Computational Materials Science. 2023. link Times cited: 0 USED (low confidence) S. Markelj et al., “The effect of nanocrystalline microstructure on deuterium transport in displacement damaged tungsten,” Nuclear Materials and Energy. 2023. link Times cited: 0 USED (low confidence) D. Jia et al., “The helium-vacancy complexes and helium bubbles formation mechanism in chromium: a comprehensive first-principle study,” Journal of Materials Science. 2023. link Times cited: 0 USED (low confidence) H. H. Chen et al., “Surface growth, inner defects and interface mixing of Cr coating on Zr alloy irradiated by 5 MeV protons at 400°C,” Journal of Nuclear Materials. 2023. link Times cited: 0 USED (low confidence) A. Bayazitov, A. Semenov, and S. V. Dmitriev, “Simulation of the Dynamics of Supersonic N-Crowdions in fcc Lead and Nickel,” Micro. 2023. link Times cited: 0 Abstract: In the case where an interstitial atom is located in a close… read moreAbstract: In the case where an interstitial atom is located in a close-packed atomic row of the crystal lattice, it is called a crowdion. Crowdions play an important role in the processes of mass and energy transfer resulting from irradiation, severe plastic deformation, ion implantation, plasma and laser processing, etc. In this work, supersonic N-crowdions (N=1, 2) in fcc lattices of lead and nickel are studied by the method of molecular dynamics. Modeling shows that the propagation distance of a supersonic 2-crowdion in lead at a high initial velocity is less than that of a supersonic 1-crowdion. In other fcc metals studied, including nickel, supersonic 2-crowdions have a longer propagation distance than 1-crowdions. The relatively short propagation distance of supersonic 2-crowdions in lead is due to their instability and rapid transformation into supersonic 1-crowdions. This feature of the dynamics of supersonic N-crowdions in lead explains its high radiation-shielding properties. read less USED (low confidence) Y. Li and W. Qiang, “Defect properties of a body-centered cubic equiatomic TiVZrTa high-entropy alloy from atomistic simulations,” Journal of Physics: Condensed Matter. 2023. link Times cited: 1 Abstract: TiVZrTa high-entropy alloys (HEAs) have been experimentally … read moreAbstract: TiVZrTa high-entropy alloys (HEAs) have been experimentally proven to exhibit excellent irradiation tolerance. In this work, defect energies and evolution were studied to reveal the underlying mechanisms of the excellent irradiation tolerance in TiVZrTa HEA via molecular statics calculations and molecular dynamics simulations. The atomic size mismatch of TiVZrTa is ∼6%, suggesting a larger lattice distortion compared to most face-centered cubic and body-centered cubic M/HEAs. Compared to pure Ta and V, smaller vacancy formation and migration energies with large energy spreads lead to higher equilibrium vacancy concentration and faster vacancy diffusion via low-energy migration paths. Vacancies in TiVZrTa have weaker abilities to form large vacancy clusters and prefer to form small clusters, indicating excellent resistance to radiation swelling. The formation energies of different types of dumbbells in TiVZrTa show significant differences and have large energy spreads. The binding abilities of interstitials in TiVZrTa are weaker compared to that in pure Ta and V. In TiVZrTa, fast vacancy diffusion and slow interstitial diffusion result in closer mobilities of vacancies and interstitials, significantly promoting point defect recombination. We further studied the effects of short-range ordered structures (SROs) on defect diffusion and evolution. SROs in TiVZrTa can effectively lead to higher fractions of defect recombination and fewer surviving defects. Our findings provide a comprehensive understanding of the underlying mechanisms of the high irradiation tolerance in body-centered cubic HEAs with large lattice distortion and suggest SROs are beneficial microstructures for enhancing irradiation tolerance. read less USED (low confidence) D. Mason, D. Nguyen-Manh, V. W. Lindblad, F. Granberg, and M. Lavrentiev, “An empirical potential for simulating hydrogen isotope retention in highly irradiated tungsten,” Journal of Physics: Condensed Matter. 2023. link Times cited: 0 Abstract: We describe the parameterization of a tungsten-hydrogen empi… read moreAbstract: We describe the parameterization of a tungsten-hydrogen empirical potential designed for use with large-scale molecular dynamics simulations of highly irradiated tungsten containing hydrogen isotope atoms, and report test results. Particular attention has been paid to getting good elastic properties, including the relaxation volumes of small defect clusters, and to the interaction energy between hydrogen isotopes and typical irradiation-induced defects in tungsten. We conclude that the energy ordering of defects changes with the ratio of H atoms to point defects, indicating that this potential is suitable for exploring mechanisms of trap mutation, including vacancy loop to plate-like void transformations. read less USED (low confidence) C. Zhang, Q. Zheng, Y. Li, L. Wei, F. Cheng, and Z. Zeng, “Fast generation of reliable primary radiation damage of BCC tungsten by sampling molecular dynamics databases,” Nuclear Materials and Energy. 2023. link Times cited: 0 USED (low confidence) V. Fotopoulos et al., “Structure and Migration Mechanisms of Small Vacancy Clusters in Cu: A Combined EAM and DFT Study,” Nanomaterials. 2023. link Times cited: 0 Abstract: Voids in face-centered cubic (fcc) metals are commonly assum… read moreAbstract: Voids in face-centered cubic (fcc) metals are commonly assumed to form via the aggregation of vacancies; however, the mechanisms of vacancy clustering and diffusion are not fully understood. In this study, we use computational modeling to provide a detailed insight into the structures and formation energies of primary vacancy clusters, mechanisms and barriers for their migration in bulk copper, and how these properties are affected at simple grain boundaries. The calculations were carried out using embedded atom method (EAM) potentials and density functional theory (DFT) and employed the site-occupation disorder code (SOD), the activation relaxation technique nouveau (ARTn) and the knowledge led master code (KLMC). We investigate stable structures and migration paths and barriers for clusters of up to six vacancies. The migration of vacancy clusters occurs via hops of individual constituent vacancies with di-vacancies having a significantly smaller migration barrier than mono-vacancies and other clusters. This barrier is further reduced when di-vacancies interact with grain boundaries. This interaction leads to the formation of self-interstitial atoms and introduces significant changes into the boundary structure. Tetra-, penta-, and hexa-vacancy clusters exhibit increasingly complex migration paths and higher barriers than smaller clusters. Finally, a direct comparison with the DFT results shows that EAM can accurately describe the vacancy-induced relaxation effects in the Cu bulk and in grain boundaries. Significant discrepancies between the two methods were found in structures with a higher number of low-coordinated atoms, such as penta-vacancies and di-vacancy absortion by grain boundary. These results will be useful for modeling the mechanisms of diffusion of complex defect structures and provide further insights into the structural evolution of metal films under thermal and mechanical stress. read less USED (low confidence) Y. Qian, M. Gilbert, L. Dezerald, D. Nguyen-Manh, and D. Cereceda, “Ab initio study of tungsten-based alloys under fusion power-plant conditions,” Journal of Nuclear Materials. 2023. link Times cited: 0 USED (low confidence) “The structure and energy of symmetric tilt grain boundaries in tungsten,” Journal of Nuclear Materials. 2023. link Times cited: 1 USED (low confidence) Y. Li, D. Yang, and W. Qiang, “Atomistic simulations of enhanced irradiation resistance and defect properties in body-centered cubic W-V-Cr and W-Ta-V alloys,” Journal of Alloys and Compounds. 2023. link Times cited: 2 USED (low confidence) L. Liu et al., “Displacement cascades database from molecular dynamic simulations in tungsten,” Journal of Nuclear Materials. 2023. link Times cited: 1 USED (low confidence) Y. Wang, J. Zhang, C. Wang, and N. Jin, “First-Principles Study of the Behaviors of He Atoms at Tic(110)/V(110) Interface,” SSRN Electronic Journal. 2023. link Times cited: 0 USED (low confidence) P. Olsson, P. Hiremath, and S. Melin, “Atomistic investigation of the impact of phosphorus impurities on the tungsten grain boundary decohesion,” Computational Materials Science. 2023. link Times cited: 2 USED (low confidence) A. Sergeev, Y. O. Kondratyeva, and L. Yashina, “Anomalous Temperature Dependence of Self-Interstitial Diffusivity in Metallic Lithium and Sodium,” Materialia. 2023. link Times cited: 0 USED (low confidence) Y. Shi et al., “Helium diffusion and bubble evolution in single-phase tungsten-based W-Ta-Cr-V complex concentrated alloy,” Journal of Nuclear Materials. 2023. link Times cited: 2 USED (low confidence) R. Qiu et al., “Molecular dynamics simulations of displacement cascades in vanadium: Generation and types of dislocation loops,” Nuclear Materials and Energy. 2023. link Times cited: 1 USED (low confidence) B. Xu et al., “Atomic study of the trapped and migration patterns of point defects around screw dislocation in tungsten,” Nuclear Materials and Energy. 2023. link Times cited: 1 USED (low confidence) S. Rao, C. Woodward, and B. Akdim, “Solid solution softening and hardening in binary BCC alloys,” Acta Materialia. 2022. link Times cited: 8 USED (low confidence) I. Shepelev, D. Bachurin, E. Korznikova, and S. Dmitriev, “Highly efficient energy and mass transfer in bcc metals by supersonic 2-crowdions,” Journal of Nuclear Materials. 2022. link Times cited: 7 USED (low confidence) L. Zhou, W. He, C. He, M. Wang, and Y. Li, “The behaviors of dislocation loops punched by helium interstitials accumulation under the temperature gradient field in tungsten,” Journal of Nuclear Science and Technology. 2022. link Times cited: 0 Abstract: ABSTRACT Enormous amounts of investigations have been made t… read moreAbstract: ABSTRACT Enormous amounts of investigations have been made to understand the helium interstitials accumulation processes in tungsten, which is a promising candidate of plasma-facing materials in fusion reactors. However, the temperature gradient, which almost certainly exists in plasma-facing materials, was often neglected in previous studies. In view of this, the molecular dynamics method is employed to simulate the helium interstitials accumulation processes in tungsten at temperature gradient field in this study. The results show that in the temperature gradient field, the helium bubble formed by helium interstitials accumulation processes also grows via punching out 1/2<111> dislocation loops, which is similar to that at constant temperature. However, under the temperature gradient field, 1/2<111> dislocation loops always were emitted to the higher-temperature region. Combined with the first principle calculation, the formation energy of self-interstitial atom at high temperature should be responsible for this phenomenon. GRAPHICAL ABSTRACT read less USED (low confidence) J. Chapman and P. Ma, “A machine-learned spin-lattice potential for dynamic simulations of defective magnetic iron,” Scientific Reports. 2022. link Times cited: 5 USED (low confidence) Z. Cao et al., “Influence of titanium on the clustering of vacancy, rhenium and osmium in tungsten-titanium alloys: First-principles study,” Fusion Engineering and Design. 2022. link Times cited: 1 USED (low confidence) I. Shepelev, I. D. Kolesnikov, and E. Korznikova, “Analysis of a crowdion propagated in an extremely heated tungsten,” Saratov Fall Meeting. 2022. link Times cited: 0 Abstract: Crowdion as one of types of an interstitial mobile defect pr… read moreAbstract: Crowdion as one of types of an interstitial mobile defect propagating in close-packed crystallographic directions can play an important role in relaxation processes occurring in bcc lattices of tungsten in nonequilibrium conditions. The crowdions is an effectively transport of mass and energy in the metal. Tungsten is considered one of the best options as a plasma-oriented material which can be exposed to ion irradiation in nuclear reactors. Recently dynamics of crowdions has been extensively studied for different types of lattices and dimensions. However, the point of energy exchange between crowdions has not been considered earlier. The paper presents an analysis of energy exchange in a complex of crowdions located in neighboring closely packed atomic row. Obtained results reveal that closely located crowdions can intensively transfer energy from one to another thus affecting the dynamics and scenario of defect structure evolution in the crystal. It is known that irradiation of tungsten can lead to microstructural changes, such as bubbles, pores and another types of defects. Moreover, the metal constantly at these conditions are heated up to extremely high temperature. Apparently, the crowdions play an important role in the formation of different defects inside the tungsten. And aim of this work is a numerically analysis of features of the crowdion in this highly heated metal bcc lattice. read less USED (low confidence) I. Shepelev, I. D. Kolesnikov, and E. Korznikova, “Propagation of 2-crowdion in W bcc lattice at finite temperature,” Saratov Fall Meeting. 2022. link Times cited: 0 Abstract: Crowdion presents an interstitial mobile defect propagating … read moreAbstract: Crowdion presents an interstitial mobile defect propagating in close-packed crystallographic directions and plays an important role in energy and mass transfer processes occurring in bcc tungsten lattice in non-equilibrium conditions. In the present day, tungsten remains one of the most promising plasma-oriented material, which saves its protective features even under high-intensive irradiation influence in nuclear reactors. Crowdions can be one of most possible and effective nonlinear channels of energy dissipation obtaining under irradiation. The dynamics of the crowdion in the lattice with the zero or very low temperature has been already deeply studied. At the same time, influence of thermal oscillations of atoms on the crowdion dynamics has not been studied in detail, despite the processes of irradiation always occur under finite nonzero temperature. In the present work, we try to reveal changing the crowdion features under different finite temperature of the tungsten lattice. read less USED (low confidence) M. B. Salman, M. Park, and M. Banisalman, “A Molecular Dynamics Study of Tungsten’s Interstitial Dislocation Loops Formation Induced by Irradiation under Local Strain,” Solids. 2022. link Times cited: 0 Abstract: A molecular dynamics simulation was used to investigate the … read moreAbstract: A molecular dynamics simulation was used to investigate the effect of applied strain on the formation of primary defects and the probability of interstitial dislocation loops (IDLs) formation of tungsten (W) during a collision cascade event. The research investigated primary knock-on atom energies of 1, 6, 10, and 14 keV, applied on a deformed W structure (form −1.4~1.6%). The peak and surviving number of Frenkel pairs (FPs) increased with increasing tension; however, these increases were more pronounced under higher strain due to the formation of IDLs. For 10 self-interstitial atoms (SIA) lengths, the strain effect reduces the clustering energy of the IDLs by about 7 eV. In general, the current findings suggest that strain effects should be carefully considered in radiation-damaged environments, particularly in low-temperature, high-radiation-energy environments. The compressed condition may advantage materials used in high-radiation-damage devices and power systems. read less USED (low confidence) A. Sergeev, A. A. Rulev, Y. O. Kondratyeva, and L. Yashina, “Computational insight into the grain boundary structure and atomic mobility in metallic lithium,” Acta Materialia. 2022. link Times cited: 3 USED (low confidence) D. Singh, S. Rao, and J. El-Awady, “Atomistic Simulations and Theoretical Modelling of Dislocation Slip and Yield Response of Industrial Tantalum Alloys,” SSRN Electronic Journal. 2022. link Times cited: 1 USED (low confidence) D. Akzhigitov, T. Srymbetov, B. Golman, C. Spitas, and Z. Utegulov, “Applied stress anisotropy effect on melting of tungsten: molecular dynamics study,” Computational Materials Science. 2022. link Times cited: 1 USED (low confidence) L. Zhang et al., “The effects of interfaces stability on mechanical properties, thermal conductivity and helium irradiation of V/Cu nano-multilayer composite,” Materials & Design. 2022. link Times cited: 9 USED (low confidence) S. Starikov, A. R. Kuznetsov, and V. Sagaradze, “Crowdion in Deformed FCC Metal. Atomistic Modeling,” Physics of Metals and Metallography. 2021. link Times cited: 3 USED (low confidence) Z.-Z. Li et al., “Investigating the formation mechanism of void lattice in tungsten under neutron irradiation: from collision cascades to ordered nanovoids,” Acta Materialia. 2021. link Times cited: 17 USED (low confidence) Y. Zhang et al., “He nanobubble driven W surface growth during low-energy He ion irradiations,” Journal of Nuclear Materials. 2021. link Times cited: 4 USED (low confidence) J. Fang, L. Liu, N. Gao, W. Hu, and H. Deng, “Molecular dynamics simulation of the behavior of typical radiation defects under stress gradient field in tungsten,” Journal of Applied Physics. 2021. link Times cited: 6 Abstract: In the fusion environment, a complex stress field is generat… read moreAbstract: In the fusion environment, a complex stress field is generated in materials, which affects the evolution of radiation defects. In this study, the behaviors of radiation-induced defects under the effect of stress gradient field in tungsten are carefully simulated at the atomic scale with the molecular dynamics (MD) method. It was found that the stress gradient field affects the migration properties of interstitial defects, resulting in the energy barriers changing with the stress and stress gradient. In the axial stress gradient field, the movement of the 1/2 interstitial dislocation loop is significantly accelerated, and it tends to move toward the region where the stress is concentrated. Within the time scale of the classical MD simulation, the stress gradient has little effect on the migration of vacancies. These results suggested that the stress gradient would cause interstitial defects to accumulate to the region where the stress is concentrated, thereby significantly changing the properties of the tungsten materials. read less USED (low confidence) P. Zhang, M. Wei, Y. Li, J. Zhao, P. Zheng, and J. Chen, “Interactions of solute atoms with self-interstitial atoms/clusters in vanadium: A first-principles study,” Journal of Nuclear Materials. 2021. link Times cited: 7 USED (low confidence) F. Granberg, J. Byggmästar, and K. Nordlund, “Molecular dynamics simulations of high-dose damage production and defect evolution in tungsten,” Journal of Nuclear Materials. 2021. link Times cited: 23 USED (low confidence) A. Backer, C. Becquart, P. Olsson, and C. Domain, “Modelling the primary damage in Fe and W: influence of the short-range interactions on the cascade properties: Part 2 – multivariate multiple linear regression analysis of displacement cascades,” Journal of Nuclear Materials. 2021. link Times cited: 10 USED (low confidence) W. Wei, C. Wu, J. L. Fan, and H. Gong, “Fundamental effects of copper on dislocation loops and mechanical property of tungsten under irradiation,” Journal of Nuclear Materials. 2021. link Times cited: 4 USED (low confidence) C. Becquart, A. D. Backer, P. Olsson, and C. Domain, “Modelling the primary damage in Fe and W: Influence of the short range interactions on the cascade properties: Part 1 – Energy transfer,” Journal of Nuclear Materials. 2021. link Times cited: 9 USED (low confidence) P. Hou 侯 et al., “Influence of helium on the evolution of irradiation-induced defects in tungsten: An object kinetic Monte Carlo simulation,” Chinese Physics B. 2021. link Times cited: 0 Abstract: Understanding the evolution of irradiation-induced defects i… read moreAbstract: Understanding the evolution of irradiation-induced defects is of critical importance for the performance estimation of nuclear materials under irradiation. Hereby, we systematically investigate the influence of He on the evolution of Frenkel pairs and collision cascades in tungsten (W) via using the object kinetic Monte Carlo (OKMC) method. Our findings suggest that the presence of He has significant effect on the evolution of irradiation-induced defects. On the one hand, the presence of He can facilitate the recombination of vacancies and self-interstitial atoms (SIAs) in W. This can be attributed to the formation of immobile He-SIA complexes, which increases the annihilation probability of vacancies and SIAs. On the other hand, due to the high stability and low mobility of He-vacancy complexes, the growth of large vacancy clusters in W is kinetically suppressed by He addition. Specially, in comparison with the injection of collision cascades and He in sequential way at 1223 K, the average sizes of surviving vacancy clusters in W via simultaneous way are smaller, which is in good agreement with previous experimental observations. These results advocate that the impurity with low concentration has significant effect on the evolution of irradiation-induced defects in materials, and contributes to our understanding of W performance under irradiation. read less USED (low confidence) J. Hou, Y. You, X.-S. Kong, J. Song, and C. Liu, “Accurate prediction of vacancy cluster structures and energetics in bcc transition metals,” Acta Materialia. 2021. link Times cited: 18 USED (low confidence) I. Shepelev, D. Bachurin, E. Korznikova, A. Bayazitov, and S. Dmitriev, “Mechanism of remote vacancy emergence by a supersonic crowdion cluster in a 2D Morse lattice,” Chinese Journal of Physics. 2021. link Times cited: 9 USED (low confidence) J. Zhang, N. Jin, L. Lian, Z. Cao, and D. Zhuang, “The behaviors of He atoms and vacancies at TiO/V interface: A first-principles study,” Applied Surface Science. 2021. link Times cited: 3 USED (low confidence) H. Wang et al., “Anisotropic interaction between self-interstitial atoms and 1/2<111> dislocation loops in tungsten,” Science China Physics, Mechanics & Astronomy. 2021. link Times cited: 2 USED (low confidence) P. Zhang, J. Zhao, T. Zou, R. Li, P. Zheng, and J. Chen, “A review of solute-point defect interactions in vanadium and its alloys: first-principles modeling and simulation,” Tungsten. 2021. link Times cited: 8 USED (low confidence) Y. Li et al., “In-situ TEM investigation of 30 keV he+ irradiated tungsten: Effects of temperature, fluence, and sample thickness on dislocation loop evolution,” Acta Materialia. 2021. link Times cited: 46 USED (low confidence) S. Rao, C. Woodward, B. Akdim, O. Senkov, and D. Miracle, “Theory of solid solution strengthening of BCC Chemically Complex Alloys,” Acta Materialia. 2021. link Times cited: 43 USED (low confidence) V. Tuli, A. Claisse, L. Messina, and P. A. Burr, “Solubility and vacancy-mediated inter-diffusion in the Zr-Nb-Cr system,” Journal of Nuclear Materials. 2021. link Times cited: 3 USED (low confidence) J. Wang, Q. Hou, and B. L. Zhang, “Migration behavior of self-interstitial defects in tungsten and iron,” Solid State Communications. 2021. link Times cited: 4 USED (low confidence) D. Singh, P. Sharma, and A. Parashar, “Atomistic simulations to study point defect dynamics in bi-crystalline niobium,” Materials Chemistry and Physics. 2020. link Times cited: 7 USED (low confidence) I. Shepelev, S. Dmitriev, A. A. Kudreyko, M. Velarde, and E. Korznikova, “Supersonic voidions in 2D Morse lattice,” Chaos Solitons & Fractals. 2020. link Times cited: 24 USED (low confidence) P. Ma, D. Mason, and S. Dudarev, “Multiscale analysis of dislocation loops and voids in tungsten,” Physical Review Materials. 2020. link Times cited: 17 Abstract: We performed ab initio density functional theory simulations… read moreAbstract: We performed ab initio density functional theory simulations of $\frac{1}{2}\ensuremath{\langle}111\ensuremath{\rangle}$ interstitial dislocation loops, closed and open vacancy loops, $\ensuremath{\langle}100\ensuremath{\rangle}$ interstitial loops, and voids in tungsten, using simulation cells involving from 2000 to 2700 atoms. The size of the loops transcends the microscopic scale and reaches the mesoscopic scale where asymptotic elasticity treatment applies. Comparing the formation energies of dislocation vacancy loops and voids, we conclude that a void remains the most energetically favorable vacancy defect over the entire range of sizes investigated here. A closed $\frac{1}{2}\ensuremath{\langle}111\ensuremath{\rangle}$ vacancy loop is more stable than an open loop if the number of vacancies in the loop is greater than $\ensuremath{\sim}45$, corresponding to the diameter of a loop of approximately 1.8 nm. We have also computed elastic dipole tensors and relaxation volumes of loops and voids, representing the source terms in continuum models for radiation induced stresses and strains in the material. A detailed analysis of metastable configurations of closed and open vacancy loops performed using molecular statics simulations shows that vacancy loop configurations are not unique, and significant fluctuations of defect structures may occur in the course of microstructural evolution under irradiation. read less USED (low confidence) P. Zhang, Y. Li, and J. Zhao, “Materials selection for nuclear applications in view of divacancy energies by comprehensive first-principles calculations,” Journal of Nuclear Materials. 2020. link Times cited: 5 USED (low confidence) D. Fernández-Pello, J. M. Fernández-Díaz, M. A. Cerdeira, C. González, and R. Iglesias, “Energetic, electronic and structural DFT analysis of point defects in refractory BCC metals,” Materials today communications. 2020. link Times cited: 1 USED (low confidence) A. Semenov and E. Koptelov, “Absence of random voids in the spatially ordered void ensemble,” Journal of Nuclear Materials. 2020. link Times cited: 0 USED (low confidence) D. Akzhigitov, T. Srymbetov, B. Golman, C. Spitas, and Z. Utegulov, “Melting of tungsten under uniaxial and shear stresses: molecular dynamics simulation,” Modelling and Simulation in Materials Science and Engineering. 2020. link Times cited: 2 Abstract: Understanding melting processes in refractory materials unde… read moreAbstract: Understanding melting processes in refractory materials under external stresses is important and can be of particular interest in harsh environment applications ranging from aerospace to nuclear and fusion energy where these materials have to simultaneously withstand the effect of high temperatures and complex stress states in such ways, that a melting process might be initiated in extreme conditions. However, most if not all of the prior research was focused on melting phenomena in the presence of hydrostatic compression. In our work, we investigate melting phenomena in pure tungsten under uniaxial tension, uniaxial compression, hydrostatic tension, and shear stress states. We explore these relationships numerically by molecular dynamics simulations employing extended Finnis–Sinclair (EFS) potential and two-phase method and compare our results with theoretical and experimental findings reported in the literature. The melting behaviour was investigated for all the studied stress states and compared both quantitatively and qualitatively on the basis of equivalent strain, Cauchy stress tensor invariants, and maximum shear stress. For uniaxial tension, hydrostatic tension, and shear stress an abrupt decline of stress-induced melting point values was detected after certain critical stress values. New high-temperature thermo-mechanical results are correlated with intricate structural changes taking place on the atomic scale during metal-melt phase transition. read less USED (low confidence) Q. Yu et al., “Understanding hydrogen retention in damaged tungsten using experimentally-guided models of complex multispecies evolution,” Nuclear Fusion. 2020. link Times cited: 11 Abstract: Fuel retention in plasma facing tungsten components is a cri… read moreAbstract: Fuel retention in plasma facing tungsten components is a critical phenomenon affecting the mechanical integrity and radiological safety of fusion reactors. It is known that hydrogen can become trapped in small defect clusters, internal surfaces, dislocations, and/or impurities, and so it is common practice to seed W subsurfaces with irradiation defects in an attempt to precondition the system to absorb hydrogen. The amount of H can later be tallied by performing careful thermal desorption tests where released temperature peaks are mapped to specific binding energies of hydrogen to defect clusters and/or microstructural features of the material. While this provides useful information about the potential trapping processes, modeling can play an important role in elucidating the detailed microscopic mechanisms that lead to hydrogen retention in damaged tungsten. In this paper, we develop a detailed kinetic model of hydrogen penetration and trapping inspired by recent experiments combining ion irradiation, hydrogen plasma exposure, and thermal desorption. We use the stochastic cluster dynamics method to solve the system of coupled partial differential equations representing the mean field description of the multispecies system. The model resolves the spatial distribution of defects and hydrogen clusters during the three processes carried out experimentally and is parameterized with information from atomistic calculations. We find that the calculated thermal desorption spectra are broadly characterized by three H emission regions: (i) a low temperature one where dislocations are the main contributors to the release peaks; (ii) an intermediate one governed by hydrogen release from small overpressurized clusters with multiple overlapping peaks, and (iii) a high temperature one defined by clean isolated emission peaks from large underpressurized bubbles. These three temperature intervals are seen to largely correlate with the depth at which the clusters are found. The relevance of the ‘super abundant’ vacancy mechanism is assessed, finding that its main role is to transfer more clusters from the intermediate to the high temperature regions as its relevance increases. We find this picture to be in very good agreement with the experiments, adding confidence to the predictive potential of the models and their useto understand irradiation damage and plasma exposure effects in plasma facing components. read less USED (low confidence) V. Andrianov, K. Bedelbekova, A. N. Ozernoy, M. Vereshchak, and I. Manakova, “Mössbauer studies of 57Fe implantation in metal Ta and Mo,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2020. link Times cited: 5 USED (low confidence) L.-J. Zhang et al., “Effects of annealing temperature and layer thickness on hardening behavior in cross accumulative roll bonded Cu/Fe nanolamellar composite,” Journal of Alloys and Compounds. 2020. link Times cited: 23 USED (low confidence) S. Zhao, “Defect properties in a VTaCrW equiatomic high entropy alloy (HEA) with the body centered cubic (bcc) structure,” Journal of Materials Science & Technology. 2020. link Times cited: 67 USED (low confidence) H. Peng, B. Liu, and F. Liu, “A strategy for designing stable nanocrystalline alloys by thermo-kinetic synergy,” Journal of Materials Science & Technology. 2020. link Times cited: 20 USED (low confidence) H. Ma et al., “The curious mechanism of irradiation-induced cryogenic grain growth in tungsten thin films: A pathway to single crystals,” Acta Materialia. 2020. link Times cited: 8 USED (low confidence) L. Liu et al., “Evaluation of tungsten interatomic potentials for radiation damage simulations,” Tungsten. 2020. link Times cited: 10 USED (low confidence) C. Cheng et al., “Development and application of EAM potentials for Ti, Al and Nb with enhanced planar fault energy of Ti,” Computational Materials Science. 2020. link Times cited: 4 USED (low confidence) D. Smirnova et al., “Atomistic description of self-diffusion in molybdenum: A comparative theoretical study of non-Arrhenius behavior,” Physical Review Materials. 2020. link Times cited: 16 Abstract: According to experimental observations, the temperature depe… read moreAbstract: According to experimental observations, the temperature dependence of self-diffusion coefficient in most body-centered cubic metals (bcc) exhibits non-Arrhenius behavior. The origin of this behavio ... read less USED (low confidence) I. Shepelev, E. Korznikova, D. Bachurin, A. Semenov, A. Chetverikov, and S. Dmitriev, “Supersonic crowdion clusters in 2D Morse lattice,” Physics Letters A. 2020. link Times cited: 19 USED (low confidence) E. Fransson and P. Erhart, “Defects from phonons: Atomic transport by concerted motion in simple crystalline metals,” Acta Materialia. 2019. link Times cited: 11 USED (low confidence) A. Chartier and M. Marinica, “Rearrangement of interstitial defects in alpha-Fe under extreme condition,” Acta Materialia. 2019. link Times cited: 45 USED (low confidence) J. Fu et al., “Molecular dynamics simulations of high-energy radiation damage in W and W–Re alloys,” Journal of Nuclear Materials. 2019. link Times cited: 33 USED (low confidence) A. Kedharnath, R. Kapoor, and A. Sarkar, “Atomistic simulation of interaction of collision cascade with different types of grain boundaries in α-Fe,” Journal of Nuclear Materials. 2019. link Times cited: 14 USED (low confidence) Y. Chen et al., “The interactions between rhenium and interstitial-type defects in bulk tungsten: A combined study by molecular dynamics and molecular statics simulations,” Journal of Nuclear Materials. 2019. link Times cited: 30 USED (low confidence) R. Harrison, G. Greaves, H. Le, H. Bei, Y. Zhang, and S. Donnelly, “Chemical effects on He bubble superlattice formation in high entropy alloys,” Current Opinion in Solid State and Materials Science. 2019. link Times cited: 25 USED (low confidence) P. Ma and S. Dudarev, “Effect of stress on vacancy formation and migration in body-centered-cubic metals,” Physical Review Materials. 2019. link Times cited: 36 USED (low confidence) R. Babicheva, I. Evazzade, E. Korznikova, I. Shepelev, K. Zhou, and S. Dmitriev, “Low-energy channel for mass transfer in Pt crystal initiated by molecule impact,” Computational Materials Science. 2019. link Times cited: 25 USED (low confidence) P. Ma and S. Dudarev, “Symmetry-broken self-interstitial defects in chromium, molybdenum, and tungsten,” Physical Review Materials. 2019. link Times cited: 32 USED (low confidence) L. Chen, L. Li, H. Gong, J. Fan, and W. Li, “Irradiation effect on mechanical properties of tungsten from molecular dynamic simulation,” Materials Letters. 2019. link Times cited: 16 USED (low confidence) O. Ogorodnikova et al., “Annealing of radiation-induced defects in tungsten: Positron annihilation spectroscopy study,” Journal of Nuclear Materials. 2019. link Times cited: 30 USED (low confidence) J. Byggmästar et al., “Collision cascades overlapping with self-interstitial defect clusters in Fe and W,” Journal of Physics: Condensed Matter. 2019. link Times cited: 38 Abstract: Overlap of collision cascades with previously formed defect … read moreAbstract: Overlap of collision cascades with previously formed defect clusters become increasingly likely at radiation doses typical for materials in nuclear reactors. Using molecular dynamics, we systematically investigate the effects of different pre-existing self-interstitial clusters on the damage produced by an overlapping cascade in bcc iron and tungsten. We find that the number of new Frenkel pairs created in direct overlap with an interstitial cluster is reduced to essentially zero, when the size of the defect cluster is comparable to that of the disordered cascade volume. We develop an analytical model for this reduced defect production as a function of the spatial overlap between a cascade and a defect cluster of a given size. Furthermore, we discuss cascade-induced changes in the morphology of self-interstitial clusters, including transformations between and dislocation loops in iron and tungsten, and between C15 clusters and dislocation loops in iron. Our results provide crucial new cascade-overlap effects to be taken into account in multi-scale modelling of radiation damage in bcc metals. read less USED (low confidence) Y.-H. Li, H.-B. Zhou, Z. Wang, H. Deng, and G. Lu, “Influence of hydrostatic strain on the behaviors of rhenium and osmium in tungsten,” Journal of Nuclear Materials. 2019. link Times cited: 1 USED (low confidence) I. V. Starchenko and E. Sadanov, “FEATURES OF HELIUM COMPLEXES BEHAVIOUR NEAR THE FREE SURFACE IN TUNGSTEN,” Problems of Atomic Science and Technology. 2019. link Times cited: 0 Abstract: The formation of interstitial atoms by lattice tungsten atom… read moreAbstract: The formation of interstitial atoms by lattice tungsten atoms displacement by clusters of implanted helium, which is accompanied with the appearance of helium-vacancy complexes, was found. The stimulating effect of the free surface on the development of the processes of displacement and dissociation of complexes has been revealed. It is shown that this influence is caused by the action of image forces. The depth of the image forces was determined, which was about 2.5 nm. read less USED (low confidence) S. Das, H. Yu, E. Tarleton, and F. Hofmann, “Orientation-dependent indentation response of helium-implanted tungsten,” Applied Physics Letters. 2019. link Times cited: 14 Abstract: A literature review of studies investigating the topography … read moreAbstract: A literature review of studies investigating the topography of nano-indents in ion-implanted materials reveals seemingly inconsistent observations, with report of both pile-up and sink-in. This may be due to the crystallographic orientation of the measured sample point, which is often not considered when evaluating implantation-induced changes in the deformation response. Here we explore the orientation dependence of spherical nano-indentation in pure and helium-implanted tungsten, considering grains with , and out-of-plane orientations. Atomic force microscopy (AFM) of indents in unimplanted tungsten shows little orientation dependence. However, in the implanted material a much larger, more localised pile-up is observed for grains than for and orientations. Based on the observations for grains, we hypothesise that a large initial hardening due to helium-induced defects is followed by localised defect removal and subsequent strain softening. A crystal plasticity finite element model of the indentation process, formulated based on this hypothesis, accurately reproduces the experimentally-observed orientation-dependence of indent morphology. The results suggest that the mechanism governing the interaction of helium-induced defects with glide dislocations is orientation independent. Rather, differences in pile-up morphology are due to the relative orientations of the crystal slip systems, sample surface and spherical indenter. This highlights the importance of accounting for crystallographic orientation when probing the deformation behaviour of ion-implanted materials using nano-indentation. read less USED (low confidence) Y.-X. Feng, J. Shang, and S. Qin, “Tensile response of (1 1 0) twist grain boundaries in tungsten: A molecular dynamics study,” Computational Materials Science. 2019. link Times cited: 3 USED (low confidence) M. Wood, M. Cusentino, B. Wirth, and A. Thompson, “Data-driven material models for atomistic simulation,” Physical Review B. 2019. link Times cited: 37 Abstract: The central approximation made in classical molecular dynami… read moreAbstract: The central approximation made in classical molecular dynamics simulation of materials is the interatomic potential used to calculate the forces on the atoms. Great effort and ingenuity is required to construct viable functional forms and find accurate parametrizations for potentials using traditional approaches. Machine learning has emerged as an effective alternative approach to develop accurate and robust interatomic potentials. Starting with a very general model form, the potential is learned directly from a database of electronic structure calculations and therefore can be viewed as a multiscale link between quantum and classical atomistic simulations. Risk of inaccurate extrapolation exists outside the narrow range of time and length scales where the two methods can be directly compared. In this work, we use the spectral neighbor analysis potential (SNAP) and show how a fit can be produced with minimal interpolation errors which is also robust in extrapolating beyond training. To demonstrate the method, we have developed a tungsten-beryllium potential suitable for the full range of binary compositions. Subsequently, large-scale molecular dynamics simulations were performed of high energy Be atom implantation onto the (001) surface of solid tungsten. The machine learned W-Be potential generates a population of implantation structures consistent with quantum calculations of defect formation energies. A very shallow ($l2\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$) average Be implantation depth is predicted which may explain ITER diverter degradation in the presence of beryllium. read less USED (low confidence) M. Banisalman and T. Oda, “Atomistic simulation for strain effects on threshold displacement energies in refractory metals,” Computational Materials Science. 2019. link Times cited: 10 USED (low confidence) P. Ma and S. Dudarev, “Universality of point defect structure in body-centered cubic metals,” Physical Review Materials. 2019. link Times cited: 56 USED (low confidence) S. Das, H. Yu, E. Tarleton, and F. Hofmann, “Hardening and Strain Localisation in Helium-Ion-Implanted Tungsten,” Scientific Reports. 2018. link Times cited: 30 USED (low confidence) A. Sand, J. Byggmästar, A. Zitting, and K. Nordlund, “Defect structures and statistics in overlapping cascade damage in fusion-relevant bcc metals,” Journal of Nuclear Materials. 2018. link Times cited: 50 USED (low confidence) Z. G. Rakhmatullina, P. Kevrekidis, and S. Dmitriev, “Non-symmetric kinks in Klein-Gordon chains free of the Peierls-Nabarro potential,” IOP Conference Series: Materials Science and Engineering. 2018. link Times cited: 1 Abstract: There exist several approaches to discretize Klein-Gordon fi… read moreAbstract: There exist several approaches to discretize Klein-Gordon field equations in a way that static kink solutions can be obtained from a two-point map, iteratively, starting from any admissible initial value. Such kinks can be placed anywhere with respect to the lattice, in other words, they do not experience the Peierls-Nabarro potential (PNP). So far, to the best of our knowledge, only symmetric PNP-free kinks have been analyzed for the φ 4 and sine-Gordon equations. It is interesting to construct PNP-free discretisations for the φ 6 equation supporting asymmetric kinks. In the present study, two versions of such discretisations are derived. read less USED (low confidence) X. Gao, G. Zhang, L. Luo, and X. Wang, “The effects of Ti and Cr on binding and diffusion of Al in V alloys: A first-principles study,” Computational Materials Science. 2018. link Times cited: 6 USED (low confidence) A. Mannheim, J. V. Dommelen, and M. Geers, “Modelling recrystallization and grain growth of tungsten induced by neutron displacement defects,” Mechanics of Materials. 2018. link Times cited: 18 USED (low confidence) J. Fikar, R. Schäublin, D. Mason, and D. Nguyen-Manh, “Nano-sized prismatic vacancy dislocation loops and vacancy clusters in tungsten,” Nuclear Materials and Energy. 2018. link Times cited: 18 USED (low confidence) Y.-X. Feng, J. Shang, S. Qin, G. Lu, and Y. Chen, “Twin and dislocation mechanisms in tensile W single crystal with temperature change: a molecular dynamics study.,” Physical chemistry chemical physics : PCCP. 2018. link Times cited: 18 Abstract: Molecular dynamics simulations are performed to investigate … read moreAbstract: Molecular dynamics simulations are performed to investigate the orientation and temperature dependence of tensile response in single crystal W. It is found that W single crystal exhibits distinct temperature-dependent deformation behaviors along different orientations. With increasing temperature, the yield strain in the [001] orientation increases, while those in [110] and [111] orientations first increase and then decrease. The tensile deformations along orientations close to [001] are found to be dominated by twinning; the nucleation and growth of twins are accomplished through the nucleation and glide of ⅙111 partial dislocations on {112} planes. In contrast, the deformations along orientations close to [110] and [111] are found to be dominated by the slip of ½111 full dislocations, which move in a stay-and-go fashion. Moreover, intermediate deformation behaviors, which may become unstable at high temperatures, are observed for some intervening orientations. The distinct deformation behaviors of W along different orientations are rationalized based on the twinning-antitwinning asymmetry of ⅙111 partial dislocations on {112} planes. read less USED (low confidence) Y.-H. Li, H.-B. Zhou, H. Deng, G. Lu, and G.-H. Lu, “Towards understanding the mechanism of rhenium and osmium precipitation in tungsten and its implication for tungsten-based alloys,” Journal of Nuclear Materials. 2018. link Times cited: 27 USED (low confidence) M. Jin, C. Permann, and M. Short, “Breaking the power law: Multiscale simulations of self-ion irradiated tungsten,” Journal of Nuclear Materials. 2018. link Times cited: 9 USED (low confidence) S. V. Dmitriev, S. V. Dmitriev, E. Korznikova, and A. Chetverikov, “Supersonic N-Crowdions in a Two-Dimensional Morse Crystal,” Journal of Experimental and Theoretical Physics. 2018. link Times cited: 28 USED (low confidence) Y. Chen et al., “New interatomic potentials of W, Re and W-Re alloy for radiation defects,” Journal of Nuclear Materials. 2018. link Times cited: 54 USED (low confidence) S. Bukkuru, U. Bhardwaj, K. S. Rao, A. Rao, M. Warrier, and M. C. Valsakumar, “Kinetics of self-interstitial migration in bcc and fcc transition metals,” Materials Research Express. 2018. link Times cited: 11 Abstract: Radiation damage is a multi-scale phenomenon. A thorough und… read moreAbstract: Radiation damage is a multi-scale phenomenon. A thorough understanding of diffusivities and the migration energies of defects is a pre-requisite to quantify the after-effects of irradiation. We investigate the thermally activated mobility of self-interstitial atom (SIA) in bcc transition metals Fe, Mo, Nb and fcc transition metals Ag, Cu, Ni, Pt using molecular dynamics (MD) simulations. The self-interstitial diffusion involves various mechanisms such as interstitialcy, dumbbell or crowdion mechanisms. Max-Space Clustering (MSC) method has been employed to identify the interstitial and its configuration over a wide range of temperature. The self-interstitial diffusion is Arrhenius like, however, there is a slight deviation at high temperatures. The migration energies, pre-exponential factors of diffusion and jump-correlation factors, obtained from these simulations can be used as inputs to Monte Carlo simulations of defect transport. The jump-correlation factor shows the degree of preference of rectilinear or rotational jumps. We obtain the average jump-correlation factor of 1.4 for bcc metals and 0.44 for fcc metals. It indicates that rectilinear jumps are preferred in bcc metals and rotational jumps are preferred in fcc metals. read less USED (low confidence) S. Dudarev and P. Ma, “Elastic fields, dipole tensors, and interaction between self-interstitial atom defects in bcc transition metals,” Physical Review Materials. 2018. link Times cited: 49 USED (low confidence) S. Starikov, L. Kolotova, A. Kuksin, D. Smirnova, and V. Tseplyaev, “Atomistic simulation of cubic and tetragonal phases of U-Mo alloy: Structure and thermodynamic properties,” Journal of Nuclear Materials. 2018. link Times cited: 46 USED (low confidence) A. Kohnert, M. Cusentino, and B. Wirth, “Molecular statics calculations of the biases and point defect capture volumes of small cavities,” Journal of Nuclear Materials. 2018. link Times cited: 16 USED (low confidence) A. Chetverikov, I. Shepelev, E. Korznikova, A. Kistanov, S. Dmitriev, and M. Velarde, “Breathing subsonic crowdion in Morse lattices,” Computational Condensed Matter. 2017. link Times cited: 31 USED (low confidence) S. Wen et al., “The study of defect structure in tungsten: Rotation and migration property for the self-interstitial atoms,” Fusion Engineering and Design. 2017. link Times cited: 6 USED (low confidence) M. Banisalman, S. Park, and T. Oda, “Evaluation of the threshold displacement energy in tungsten by molecular dynamics calculations,” Journal of Nuclear Materials. 2017. link Times cited: 31 USED (low confidence) S. Dmitriev, N. Medvedev, A. Chetverikov, K. Zhou, and M. Velarde, “Highly Enhanced Transport by Supersonic N‐Crowdions,” physica status solidi (RRL) – Rapid Research Letters. 2017. link Times cited: 28 Abstract: An interstitial atom placed in a close‐packed atomic row of … read moreAbstract: An interstitial atom placed in a close‐packed atomic row of a crystal is called crowdion. Such defects are highly mobile, they can move along the row transporting mass and energy. In the present study the concept of the classical supersonic crowdion is generalized to N‐crowdion in which not one but N atoms move simultaneously at a high speed. With the help of molecular dynamics simulations for fcc Morse crystal it is demonstrated that N‐crowdions are much more efficient in mass transport being able to propagate through larger distances having smaller total energy than the classical 1‐crowdion. read less USED (low confidence) P. Zhang, J. Ding, D. Sun, and J. Zhao, “First-principles study of noble gas atoms in bcc Fe,” Journal of Nuclear Materials. 2017. link Times cited: 14 USED (low confidence) Z. Zhao, Y. Li, C. Zhang, G. Pan, P. Tang, and Z. Zeng, “Effect of grain size on the behavior of hydrogen/helium retention in tungsten: a cluster dynamics modeling,” Nuclear Fusion. 2017. link Times cited: 25 Abstract: Reducing ion retention in materials is a key factor in the m… read moreAbstract: Reducing ion retention in materials is a key factor in the management of tritium inventory, the selection of compatible plasma-facing materials (PFMs), and thus the future development of fusion reactors. In this work, by introducing the cellular sink strength of grain boundaries (GBs) into the cluster dynamics model, the behavior of hydrogen (H) and helium (He) retention in W with different grain sizes is studied under various irradiation conditions systematically. It is found that the H/He retention increases dramatically with decreasing grain size at typical service temperatures, due to the enhancement of H/He capture ratio by GBs. Generally, He retention exists in three forms: He in GBs, in dislocations and in clusters (HemVn, Hen and HenI). Our further study shows that, under the irradiation of low energy and low fluence ions, the contribution of He in clusters is negligible. The total He retention is thus dominated by the competing absorption of GBs and dislocations, that is, changing from the dislocation-based to grain boundary-based retention with decreasing grain size. H retention also presents the same behavior. In view of these grain size-related behaviors of H/He retention in W, it is suggested that coarse-grained crystals should be selected for W-based PFMs in practice. read less USED (low confidence) I.-T. Lu and M. Bernardi, “Using defects to store energy in materials – a computational study,” Scientific Reports. 2017. link Times cited: 16 USED (low confidence) V. Svetukhin and M. Tikhonchev, “Effective Atomic Displacements in Fe-9at.%Cr Alloy,” Defect and Diffusion Forum. 2017. link Times cited: 2 Abstract: A computer simulation of atomic displacement cascades in Fe-… read moreAbstract: A computer simulation of atomic displacement cascades in Fe-9at.%Cr binary alloy has been performed by molecular dynamics method for temperature of 300 K and cascade energies from 100 eV to 20 keV. The average number of Frenkel pairs produced in cascade has been calculated. The data on point defect clusterization have been obtained. Obtained evaluations of effective fraction of surviving defects are well approximated by the sum of power and linear functions of cascade energy. Increased chromium fraction in the self-interstitial (SIA) configurations has been observed and has been explained by combination of two factors: positive binding energy of Cr atom with SIAs and mobility of SIA configuration. The diffusion coefficient of single SIA configuration in the matrix of pure bcc Fe has been evaluated for the temperature range of 300 – 1000 K. We have prepared 100 group neutron cross-sections of effective displacement generation in Fe-9at.%Cr binary alloy. It has been shown that effective dpa generation rate can be 2-3 times lower than corresponding rates of conventional dpa generation rate. read less USED (low confidence) Y.-X. Feng, J. Shang, and G. Lu, “Migration and nucleation of helium atoms at (110) twist grain boundaries in tungsten,” Journal of Nuclear Materials. 2017. link Times cited: 14 USED (low confidence) M. Lavrentiev, D. Nguyen-Manh, and S. Dudarev, “Chromium-vacancy clusters in dilute bcc Fe-Cr alloys: an ab initio study,” arXiv: Materials Science. 2017. link Times cited: 12 USED (low confidence) J. Fikar, R. Gröger, and R. Schäublin, “Interaction of irradiation-induced prismatic dislocation loops with free surfaces in tungsten,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2017. link Times cited: 16 USED (low confidence) J. Chai et al., “First-principles investigation of the energetics of point defects at a grain boundary in tungsten,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2017. link Times cited: 16 USED (low confidence) B. Fu, S. Fitzgerald, Q. Hou, J. Wang, and M. Li, “Effect of collision cascades on dislocations in tungsten: A molecular dynamics study,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2017. link Times cited: 25 USED (low confidence) P. Grigorev, A. Bakaev, D. Terentyev, G. Oost, J. Noterdaeme, and E. Zhurkin, “Interaction of hydrogen and helium with nanometric dislocation loops in tungsten assessed by atomistic calculations,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2017. link Times cited: 14 USED (low confidence) G. Bonny et al., “Density functional theory-based cluster expansion to simulate thermal annealing in FeCrW alloys,” Philosophical Magazine. 2017. link Times cited: 10 Abstract: In this work, we develop a rigid lattice cluster expansion a… read moreAbstract: In this work, we develop a rigid lattice cluster expansion as an ultimate goal to track the micro-structural evolution of Eurofer steel under neutron irradiation. The fact that all (defect) structures are mapped upon a rigid lattice allows a simplified computation and fitting procedure, thus enabling alloys of large chemical complexity to be modelled. As a first step towards the chemical complexity of Eurofer steels, we develop a cluster expansion (CE) for the FeCrW-vacancy system based on density functional theory (DFT) calculations in the dilute alloy limit. The DFT calculations suggest that only CrW clusters containing vacancies are stabilised. The cluster expansion was used to simulate thermal annealing in Fe–20Cr–xW alloys at 773 K. It is found that the addition of W to the alloy results in a non-linear decrease in the precipitation kinetics. The CE was found suitable to describe the energetics of the FeCrW-vacancy system in the Fe-rich limit. read less USED (low confidence) G. Samolyuk, Y. Osetsky, and R. Stoller, “Properties of Vacancy Complexes with Hydrogen and Helium Atoms in Tungsten from First Principles,” Fusion Science and Technology. 2017. link Times cited: 16 Abstract: Tungsten and its alloys are the primary candidate materials … read moreAbstract: Tungsten and its alloys are the primary candidate materials for plasma-facing components in fusion reactors. The material is exposed to high-energy neutrons and the high flux of helium and hydrogen atoms. In this work we have studied the properties of vacancy clusters and their interaction with H and He in W using density functional theory. Convergence of calculations with respect to modeling cell size was investigated. It is demonstrated that vacancy cluster formation energy converges with small cells with a size of 6 × 6 × 6 (432 lattice sites) enough to consider a microvoid of up to six vacancies with high accuracy. Most of the vacancy clusters containing fewer than six vacancies are unstable. Introducing He or H atoms increases their binding energy potentially making gas-filled bubbles stable. According to the results of the calculations, the H2 molecule is unstable in clusters containing six or fewer vacancies. read less USED (low confidence) S. Wen et al., “First-principles study on mono-vacancy self diffusion and recovery in tungsten crystal,” Fusion Engineering and Design. 2016. link Times cited: 7 USED (low confidence) D. Wang et al., “Effect of strain field on displacement cascade in tungsten studied by molecular dynamics simulation,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2016. link Times cited: 28 USED (low confidence) R. Li et al., “Effects of Cr and W additions on the stability and migration of He in bcc Fe: A first-principles study,” Computational Materials Science. 2016. link Times cited: 19 USED (low confidence) A. V. Verkhovykh, A. Mirzoev, G. E. Ruzanova, D. Mirzaev, and K. Okishev, “Interaction of Hydrogen Atoms with Vacancies and Divacancies in bcc Iron,” Materials Science Forum. 2016. link Times cited: 6 Abstract: The paper presents the results of both ab initio and thermod… read moreAbstract: The paper presents the results of both ab initio and thermodynamic analysis of vacancy and divacancy formation and hydrogen interaction with them in alpha (bcc) iron. Ab initio calculations were performed by DFT method using LAPW in WIEN2k package. Monovacancy formation energy was found to be 2.15 eV and divacancy binding energy 0.22 ± 0.01 eV. Equlibrium fraction of vacancies bound into divacancies is of the order of 10–5 even at the highest temperatures close to bcc → fcc transformation point. Hydrogen has a strong interaction with monovacancies (vacancy-hydrogen binding energy decreasing from 0.60 to 0.31 eV for the first–fifth H atom inside a single vacancy) but has only a small effect on divacancy formation energy that is equal to 0.28, 0.19 and 0.17 for the case of joining of VH + V, VH + VH and VH2 + VH2, respectively. This means that the presence of hydrogen cannot significantly increase the equilibrium concentration of divacancies. read less USED (low confidence) M. A. Cerdeira, S. L. Palacios, C. González, D. Fernández-Pello, and R. Iglesias, “Ab initio simulations of the structure, energetics and mobility of radiation-induced point defects in bcc Nb,” Journal of Nuclear Materials. 2016. link Times cited: 17 USED (low confidence) V. Sagaradze, V. Shabashov, N. Kataeva, K. A. Kozlov, A. R. Kuznetsov, and A. V. Litvinov, “The anomalous diffusion processes ‘dissolution-precipitation’ of THE γ′ Phase Ni3Al in AN Fe–Ni–Al alloy during low-temperature deformation,” Materials Letters. 2016. link Times cited: 12 USED (low confidence) A. Sand, J. Dequeker, C. Becquart, C. Domain, and K. Nordlund, “Non-equilibrium properties of interatomic potentials in cascade simulations in tungsten,” Journal of Nuclear Materials. 2016. link Times cited: 60 USED (low confidence) J. Dérès, L. Proville, and M. Marinica, “Dislocation depinning from nano-sized irradiation defects in a bcc iron model,” Acta Materialia. 2015. link Times cited: 23 USED (low confidence) R. Kobayashi, T. Hattori, T. Tamura, and S. Ogata, “A molecular dynamics study on bubble growth in tungsten under helium irradiation,” Journal of Nuclear Materials. 2015. link Times cited: 50 USED (low confidence) N. Fernandez, Y. Ferro, and D. Kato, “Hydrogen diffusion and vacancies formation in tungsten: Density Functional Theory calculations and statistical models,” Acta Materialia. 2015. link Times cited: 168 USED (low confidence) B. Wirth, X. Hu, A. Kohnert, and D. Xu, “Modeling defect cluster evolution in irradiated structural materials: Focus on comparing to high-resolution experimental characterization studies,” Journal of Materials Research. 2015. link Times cited: 29 Abstract: It is well established that exposure of metallic structural … read moreAbstract: It is well established that exposure of metallic structural materials to irradiation environments results in significant microstructural evolution, property changes, and performance degradation, which limits the extended operation of current generation light water reactors and restricts the design of advanced fission and fusion reactors. Further, it is well recognized that these irradiation effects are a classic example of inherently multiscale phenomena and that the mix of radiation-induced features formed and the corresponding property degradation depend on a wide range of material and irradiation variables. This inherently multiscale evolution emphasizes the importance of closely integrating models with high-resolution experimental characterization of the evolving radiation-damaged microstructure. This article provides a review of recent models of the defect microstructure evolution in irradiated body-centered cubic materials, which provide good agreement with experimental measurements, and presents some outstanding challenges, which will require coordinated high-resolution characterization and modeling to resolve. read less USED (low confidence) L.-F. Wang, X. Shu, and G. Lu, “Comparison of two tungsten–helium interatomic potentials,” Journal of Materials Research. 2015. link Times cited: 4 Abstract: We have clarified the performance of two tungsten–helium ana… read moreAbstract: We have clarified the performance of two tungsten–helium analytical interatomic potentials, one of which, developed by Li et al., is a bond-order potential, and another, developed by Juslin et al., is a combination of embedded atom method potential and pair potential. Using these two potentials, we have simulated and made a full comparison of formation energy and migration energy of different defects including helium and vacancy, binding energies of helium and vacancy with helium-vacancy cluster, surface energy, as well as melting point, with reference to the corresponding results from the first-principles and experiments. read less USED (low confidence) M. Volosyuk, “The role of interstitial (crowdion) mass-transfer for crack high-temperature healing under uniaxial loading,” Functional Materials. 2015. link Times cited: 7 USED (low confidence) A. Sand, K. Nordlund, and S. Dudarev, “Radiation damage production in massive cascades initiated by fusion neutrons in tungsten,” Journal of Nuclear Materials. 2014. link Times cited: 73 USED (low confidence) C. Zhang, J. Fu, R. Li, P. Zhang, J. Zhao, and C. Dong, “Solute/impurity diffusivities in bcc Fe: A first-principles study,” Journal of Nuclear Materials. 2014. link Times cited: 16 USED (low confidence) F. Hofmann et al., “Lattice swelling and modulus change in a helium-implanted tungsten alloy: X-ray micro-diffraction, surface acoustic wave measurements, and multiscale modelling,” Acta Materialia. 2014. link Times cited: 134 USED (low confidence) A. Meinander, S. Dudarev, and K. Nordlund, “Massively parallel simulations of generation of radiation defects in very high-energy cascades in iron and tungsten: a comparative study,” International Conference on Supercomputing. 2014. link Times cited: 0 USED (low confidence) P. Zhang and J. Zhao, “Energetics and configurations of He–He pair in vacancy of transition metals,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2014. link Times cited: 9 USED (low confidence) Y. Zhou, Y. Zhou, J.-ling Wang, Q. Hou, and A. Deng, “Molecular dynamics simulations of the diffusion and coalescence of helium in tungsten,” Journal of Nuclear Materials. 2014. link Times cited: 58 USED (low confidence) V. Borovikov, A. Voter, and X. Tang, “Reflection and implantation of low energy helium with tungsten surfaces,” Journal of Nuclear Materials. 2014. link Times cited: 35 USED (low confidence) C. Zhang, P. Zhang, R. Li, J. Zhao, and C. Dong, “Stability and migration of vacancy in V-4Cr-4Ti alloy: Effects of Al, Si, Y trace elements,” Journal of Nuclear Materials. 2013. link Times cited: 17 USED (low confidence) K. Henriksson, C. Björkas, and K. Nordlund, “Atomistic simulations of stainless steels: a many-body potential for the Fe–Cr–C system,” Journal of Physics: Condensed Matter. 2013. link Times cited: 65 Abstract: Stainless steels found in real-world applications usually ha… read moreAbstract: Stainless steels found in real-world applications usually have some C content in the base Fe–Cr alloy, resulting in hard and dislocation-pinning carbides—Fe3C (cementite) and Cr23C6—being present in the finished steel product. The higher complexity of the steel microstructure has implications, for example, for the elastic properties and the evolution of defects such as Frenkel pairs and dislocations. This makes it necessary to re-evaluate the effects of basic radiation phenomena and not simply to rely on results obtained from purely metallic Fe–Cr alloys. In this report, an analytical interatomic potential parameterization in the Abell–Brenner–Tersoff form for the entire Fe–Cr–C system is presented to enable such calculations. The potential reproduces, for example, the lattice parameter(s), formation energies and elastic properties of the principal Fe and Cr carbides (Fe3C, Fe5C2, Fe7C3, Cr3C2, Cr7C3, Cr23C6), the Fe–Cr mixing energy curve, formation energies of simple C point defects in Fe and Cr, and the martensite lattice anisotropy, with fair to excellent agreement with empirical results. Tests of the predictive power of the potential show, for example, that Fe–Cr nanowires and bulk samples become elastically stiffer with increasing Cr and C concentrations. High-concentration nanowires also fracture at shorter relative elongations than wires made of pure Fe. Also, tests with Fe3C inclusions show that these act as obstacles for edge dislocations moving through otherwise pure Fe. read less USED (low confidence) R. Li, P. Zhang, C. Zhang, X. Huang, and J. Zhao, “Vacancy trapping mechanism for multiple helium in monovacancy and small void of vanadium solid,” Journal of Nuclear Materials. 2013. link Times cited: 29 USED (low confidence) M. Cak, T. Hammerschmidt, and R. Drautz, “Comparison of analytic and numerical bond-order potentials for W and Mo,” Journal of Physics: Condensed Matter. 2013. link Times cited: 4 Abstract: Bond-order potentials (BOPs) are derived from the tight-bind… read moreAbstract: Bond-order potentials (BOPs) are derived from the tight-binding approximation and provide a linearly-scaling computation of the energy and forces for a system of interacting atoms. While the numerical BOPs involve the numerical integration of the response (Green’s) function, the expressions for the energy and interatomic forces are analytical within the formalism of the analytic BOPs. In this paper we present a detailed comparison of numerical and analytic BOPs. We use established parametrizations for the bcc refractory metals W and Mo and test structural energy differences; tetragonal, trigonal, hexagonal and orthorhombic deformation paths; formation energies of point defects as well as phonon dispersion relations. We find that the numerical and analytic BOPs generally are in very good agreement for the calculation of energies. Different from the numerical BOPs, the forces in the analytic BOPs correspond exactly to the negative gradients of the energy. This makes it possible to use the analytic BOPs in dynamical simulations and leads to improved predictions of defect energies and phonons as compared to the numerical BOPs. read less USED (low confidence) A. P. Selby, D. Xu, N. Juslin, N. Capps, and B. Wirth, “Primary defect production by high energy displacement cascades in molybdenum,” Journal of Nuclear Materials. 2013. link Times cited: 14 USED (low confidence) L. Bukonte, F. Djurabekova, J. Samela, K. Nordlund, S. Norris, and M. Aziz, “Comparison of molecular dynamics and binary collision approximation simulations for atom displacement analysis,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2013. link Times cited: 52 USED (low confidence) M. Li, J. Cui, J. Wang, and Q. Hou, “Radiation damage of tungsten surfaces by low energy helium atom bombardment – A molecular dynamics study,” Journal of Nuclear Materials. 2013. link Times cited: 21 USED (low confidence) V. Borovikov, X. Tang, D. Perez, X. Bai, B. Uberuaga, and A. Voter, “Influence of point defects on grain boundary mobility in bcc tungsten,” Journal of Physics: Condensed Matter. 2013. link Times cited: 21 Abstract: Atomistic computer simulations were performed to study the i… read moreAbstract: Atomistic computer simulations were performed to study the influence of radiation-induced damage on grain boundary (GB) sliding processes in bcc tungsten (W), the divertor material in the ITER tokamak and the leading candidate for the first wall material in future fusion reactors. In particular, we calculated the average sliding-friction force as a function of the number of point defects introduced into the GB for a number of symmetric tilt GBs. In all cases the average sliding-friction force at fixed shear strain rate depends on the number of point defects introduced into the GB, and in many cases introduction of these defects reduces the average sliding-friction force by roughly an order of magnitude. We have also observed that as the number of interstitials in the GB is varied, the direction of the coupled GB motion sometimes reverses, causing the GB to migrate in the opposite direction under the same applied shear stress. This could be important in the microstructural evolution of polycrystalline W under the harsh radiation environment in a fusion reactor, in which high internal stresses are present and frequent collision cascades generate interstitials and vacancies. read less USED (low confidence) Y. Li, W. Zhou, L.-F. Huang, Z. Zeng, and X. Ju, “Cluster dynamics modeling of accumulation and diffusion of helium in neutron irradiated tungsten,” Journal of Nuclear Materials. 2012. link Times cited: 31 USED (low confidence) R. Ning, Y. Li, W. Zhou, Z. Zeng, and X. Ju, “Modeling D retention in W under D ions and neutrons irradiation,” Journal of Nuclear Materials. 2012. link Times cited: 12 USED (low confidence) D. Xu, B. Wirth, M. Li, and M. Kirk, “Defect microstructural evolution in ion irradiated metallic nanofoils: Kinetic Monte Carlo simulation versus cluster dynamics modeling and in situ transmission electron microscopy experiments,” Applied Physics Letters. 2012. link Times cited: 27 Abstract: Understanding materials degradation under intense irradiatio… read moreAbstract: Understanding materials degradation under intense irradiation is important for the development of next generation nuclear power plants. Here we demonstrate that defect microstructural evolution in molybdenum nanofoils in situ irradiated and observed on a transmission electron microscope can be reproduced with high fidelity using an object kinetic Monte Carlo (OKMC) simulation technique. Main characteristics of defect evolution predicted by OKMC, namely, defect density and size distribution as functions of foil thickness, ion fluence and flux, are in excellent agreement with those obtained from the in situ experiments and from previous continuum-based cluster dynamics modeling. The combination of advanced in situ experiments and high performance computer simulation/modeling is a unique tool to validate physical assumptions/mechanisms regarding materials response to irradiation, and to achieve the predictive power for materials stability and safety in nuclear facilities. read less USED (low confidence) J. Wang, Y. Zhou, M. Li, and Q. Hou, “Atomistic simulations of helium behavior in tungsten crystals,” Journal of Nuclear Materials. 2012. link Times cited: 29 USED (low confidence) T. Ahlgren, K. Heinola, K. Vörtler, and J. Keinonen, “Simulation of irradiation induced deuterium trapping in tungsten,” Journal of Nuclear Materials. 2012. link Times cited: 70 USED (low confidence) R. Ning, Y. Li, W. Zhou, Z. Zeng, and X. Ju, “AN IMPROVED CLUSTER DYNAMICS MODEL FOR HYDROGEN RETENTION IN TUNGSTEN,” International Journal of Modern Physics C. 2012. link Times cited: 10 Abstract: An improved cluster dynamics model has been developed for st… read moreAbstract: An improved cluster dynamics model has been developed for studying the behaviors of hydrogen retention in tungsten under hydrogen ions irradiation. In addition to different types of objects, adopting up-to-date parameters and complex reaction processes, we newly introduce ion-induced and natural defects into our model. This improved model programmed in IRadMat2 could describe very well the depth distributions and the amounts of hydrogen retained in tungsten under different radiation conditions. The calculated results agree with the experimental ones much better than the previous model, especially for the depth-distribution of D retained in W, which imply that this model is applicable to the evolution of defects especially for low energy high flux ions irradiated on plasma-facing materials. read less USED (low confidence) D. Xu, B. Wirth, M. Li, and M. Kirk, “Combining in situ transmission electron microscopy irradiation experiments with cluster dynamics modeling to study nanoscale defect agglomeration in structural metals,” Acta Materialia. 2012. link Times cited: 89 USED (low confidence) D. Xu, B. Wirth, M. Li, and M. Kirk, “Recent work towards understanding defect evolution in thin molybdenum foils through in situ ion irradiation under TEM and coordinated cluster dynamics modeling,” Current Opinion in Solid State & Materials Science. 2012. link Times cited: 8 USED (low confidence) C. Becquart and C. Domain, “Solute-point defect interactions in bcc systems: Focus on first principles modelling in W and RPV steels,” Current Opinion in Solid State & Materials Science. 2012. link Times cited: 81 USED (low confidence) P. Ma, S. Dudarev, and C. Woo, “Spin-lattice-electron dynamics simulations of magnetic materials,” Physical Review B. 2012. link Times cited: 48 Abstract: We develop a dynamic spin-lattice-electron model for simulat… read moreAbstract: We develop a dynamic spin-lattice-electron model for simulating the time-dependent evolution of coupled spin, atomic, and electronic degrees of freedom in a magnetic material. Using the model, we relate the dissipative parameters entering the Langevin equations for the lattice and spin degrees of freedom to the heat transfer coefficients of a phenomenological spin-lattice-electron three-temperature model. We apply spin-lattice-electron dynamics simulations to the interpretation of experiments on laser-induced demagnetization of iron thin films, and estimate the rates of heat transfer between the spins and electrons, and between atoms and electrons. To model the dynamics of energy dissipation in a magnetic material undergoing plastic deformation, we develop an algorithm that separates the local collective modes of motion of atoms from their random thermal motion. Using this approach, we simulate the propagation of compressive shock waves through magnetic iron. We also explore the microscopic dynamics of dissipative coupling between the spin and lattice subsystems, and show that the rate of spin-lattice heat transfer is proportional to the integral of the four-spin time-dependent correlation function. read less USED (low confidence) M. Li, J. Wang, and Q. Hou, “Molecular dynamics studies of temperature effects on low energy helium bombardments on tungsten surfaces,” Journal of Nuclear Materials. 2012. link Times cited: 27 USED (low confidence) Y. Zhang, H.-C. Huang, P. Millett, M. Tonks, D. Wolf, and S. Phillpot, “Atomistic study of grain boundary sink strength under prolonged electron irradiation.,” Journal of Nuclear Materials. 2012. link Times cited: 38 USED (low confidence) P. Zhang, J. Zhao, Y. Qin, and B. Wen, “Stability and dissolution of helium–vacancy complexes in vanadium solid,” Journal of Nuclear Materials. 2011. link Times cited: 47 USED (low confidence) D. Kato, H. Iwakiri, and K. Morishita, “Formation of vacancy clusters in tungsten crystals under hydrogen-rich condition,” Journal of Nuclear Materials. 2011. link Times cited: 38 USED (low confidence) A. L. Nikolaev and T. Kurennykh, “On the interaction between radiation-induced defects and foreign interstitial atoms in α-iron,” Journal of Nuclear Materials. 2011. link Times cited: 14 USED (low confidence) I. Valikova and A. Nazarov, “Simulation of Atomic Structure and Diffusion Characteristics of Point Defects in BCC and FCC Metals,” Solid State Phenomena. 2011. link Times cited: 3 Abstract: Our recent model has been used to evaluate the point defect … read moreAbstract: Our recent model has been used to evaluate the point defect characteristics including those determining the effect of pressure on the concentration of vacancies, di-vacancies, interstitials and their diffusion mobility in set of BCC and FCC metals. Our model has been developed to calculate temperature dependences of mentioned features. In contrast to other studies, the vacancy migration volumes have been found for all the metals studied. read less USED (low confidence) C. Becquart, C. Domain, U. Sarkar, A. Debacker, and M. Hou, “Microstructural evolution of irradiated tungsten: Ab initio parameterisation of an OKMC model,” Journal of Nuclear Materials. 2010. link Times cited: 174 USED (low confidence) R. Pasianot and V. P. Ramunni, “Small interstitials clusters migration in bcc metals: A Molybdenum model,” Computational Materials Science. 2010. link Times cited: 3 USED (low confidence) M. Gilbert and S. Dudarev, “Ab initio multi-string Frenkel–Kontorova model for a b = a/2[111] screw dislocation in bcc iron,” Philosophical Magazine. 2010. link Times cited: 23 Abstract: We formulate a multi-string Frenkel–Kontorova (MSFK) model f… read moreAbstract: We formulate a multi-string Frenkel–Kontorova (MSFK) model for a a/2[111] screw dislocation in bcc iron, and investigate the occurrence of degenerate and non-degenerate dislocation core structures as functionals of the law of interaction between the [111] strings of atoms forming the crystal. By comparing the effective inter-string interaction laws derived from ab initio density functional calculations and from semi-empirical interatomic potentials for α-iron, we show that it is the form of the function determining how the atomic strings interact with each other as a function of their relative one-dimensional displacement in the [111] direction that determines whether a degenerate or a non-degenerate screw dislocation core configuration has lower energy. We show that by constructing a one-dimensional inter-string interaction law, and by solving the MSFK equations, it is possible to easily predict the nature of the screw dislocation core, hence providing a simple yet effective check to aid the development of short-range semi-empirical interatomic potentials for bcc transition metals. Finally, we analyse the relation between the inter-string interaction law, and the shape and the height of the Peierls energy barriers separating the adjacent equilibrium configurations for a migrating screw dislocation. read less USED (low confidence) A. Iskandarov, N. Medvedev, P. Zakharov, and S. Dmitriev, “Crowdion mobility and self-focusing in 3D and 2D nickel,” Computational Materials Science. 2009. link Times cited: 21 USED (low confidence) P. Olsson, “Semi-empirical atomistic study of point defect properties in BCC transition metals,” Computational Materials Science. 2009. link Times cited: 61 USED (low confidence) M. Samaras, “Multiscale Modelling: the role of helium in iron,” Materials Today. 2009. link Times cited: 73 USED (low confidence) P. Schuck, J. Marian, J. B. Adams, and B. Sadigh, “Vibrational properties of straight dislocations in bcc and fcc metals within the harmonic approximation,” Philosophical Magazine. 2009. link Times cited: 7 Abstract: We calculate the vibrational spectra of straight screw and e… read moreAbstract: We calculate the vibrational spectra of straight screw and edge dislocations in several body-centered cubic (bcc) (Mo and Fe) and face-centered cubic (fcc) (Cu and Al) metals within the harmonic approximation. We take advantage of the translational symmetry of straight dislocations to efficiently calculate their phonon eigenstates in the harmonic limit. This allows us to calculate the low-temperature contribution of straight screw and edge dislocations to the heat capacity of each respective metal, and show that the dominant temperature dependence below 5 K is linear. Comparison with heat capacity measurements of heavily cold-worked Cu reveals very good agreement with our calculations. At higher temperatures, the contribution from the non-linear terms becomes significant. As a result, maxima in the straight dislocation heat capacities are observed in the temperature range from 9% to 16% of the Debye temperature. We investigate the appearance of localized and resonance peaks in the vibrational spectra induced by dislocations, and study in detail their spatial spread around the dislocation cores by projecting vibrational eigenstates onto individual atoms. We study the deviation of these atomic-level vibrational free energies from that of the perfect crystal as a function of distance to the dislocation cores, and establish that, similar to the dislocation energy, the vibrational free energy of an isolated dislocation behaves logarithmically in the long-range limit. Finally, we obtain vibrational spectra for propagating waves along the dislocation line and find that the dispersion for these waves is consistent with the notion of kink formation and motion for screw dislocations. read less USED (low confidence) G. Lucas and R. Schäublin, “Vibrational contributions to the stability of point defects in bcc iron: A first-principles study,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2009. link Times cited: 35 USED (low confidence) C. Björkas, K. Nordlund, and S. Dudarev, “Modelling radiation effects using the ab-initio based tungsten and vanadium potentials,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2009. link Times cited: 89 USED (low confidence) J. Fikar and R. Schäublin, “Atomistic simulations of nanometric dislocation loops in bcc tungsten,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2009. link Times cited: 20 USED (low confidence) D. Nguyen-Manh, M. Lavrentiev, and S. Dudarev, “Magnetic properties of point defect interaction with impurity atoms in Fe-Cr alloys,” Journal of Nuclear Materials. 2009. link Times cited: 7 USED (low confidence) C. Becquart and C. Domain, “An object Kinetic Monte Carlo Simulation of the dynamics of helium and point defects in tungsten,” Journal of Nuclear Materials. 2009. link Times cited: 160 USED (low confidence) B. Lipschultz, D. Whyte, J. Irby, B. LaBombard, and G. Wright, “Hydrogenic retention with high-Z plasma facing surfaces in Alcator C-Mod,” Nuclear Fusion. 2009. link Times cited: 34 Abstract: The retention of deuterium (D) fuel in the Alcator C-Mod tok… read moreAbstract: The retention of deuterium (D) fuel in the Alcator C-Mod tokamak is studied using a new ‘static’ gas balance method. C-Mod solely employs high-Z molybdenum (Mo) and tungsten (W) for its plasma facing materials, with intermittent application of thin boron (B) films. The primarily Mo surfaces are found to retain large fractions, ∼20–50%, of the D2 gas fuelled per quiescent discharge, regardless of whether the Mo surfaces are cleaned of, or partially covered by, B films. Several experiments and calculations show that it is improbable that B retains significant fractions of the fuel. Rather, retention occurs in Mo and W surfaces through ion bombardment, implantation and diffusion to trap sites. Roughly 1% D of the incident ion fluence, ΦD, to surfaces is retained, and with no indication of the retention rate decreasing after 25 s of integrated plasma exposure. The magnitude of retention is significantly larger than that extrapolated from the results of laboratory studies for either Mo or W. The high levels of D/Mo in the near surface, measured directly post-campaign (∼0.01) in tiles and inferred from gas balance, are consistent with trapping sites for fuel retention in the Mo being created, or expanded, by high D atom densities in the near surface which arise as a result of high incident ion fluxes. Differences between C-Mod and laboratory retention results may be due to such factors as the multiply ionized B ions incident on the surface directly creating traps, the condition of Mo (impurities, annealing) and the high-flux densities in the C-Mod divertor which are similar to ITER, but 10–100× those used in laboratory studies. Disruptions produce rapid heating of the surfaces, releasing trapped hydrogenic species into the vessel for recovery. The measurements of the large amount of gas released in disruptions are consistent with the analysis of tiles removed from the vessel post-campaign—the campaign-integrated retention is very low, of order 1000× less than that observed in a single, non-disruptive discharge. read less USED (low confidence) D. Nguyen-Manh, M. Lavrentiev, and S. Dudarev, “Ab initio and Monte Carlo modeling in Fe–Cr system: Magnetic origin of anomalous thermodynamic and kinetic properties,” Computational Materials Science. 2008. link Times cited: 15 USED (low confidence) D. Nguyen-Manh, M. Lavrentiev, and S. Dudarev, “The Fe–Cr system: atomistic modelling of thermodynamics and kinetics of phase transformations.” 2008. link Times cited: 50 USED (low confidence) J. Fikar and R. Schäublin, “Molecular dynamics simulation of radiation damage in bcc tungsten,” Journal of Nuclear Materials. 2007. link Times cited: 89 USED (low confidence) L. Zhang et al., “Study on thermal stability and irradiation response of copper/iron nano-multilayer composite fabricated by cross accumulative roll bonding,” Journal of Nuclear Materials. 2021. link Times cited: 13 USED (low confidence) P. Ma and S. Dudarev, “Atomistic Spin-Lattice Dynamics,” Handbook of Materials Modeling. 2020. link Times cited: 8 USED (low confidence) Z. Kaszkur, “Thermodynamical Properties of Nanoalloys,” Nanoalloys. 2020. link Times cited: 0 USED (low confidence) M. Luo, L. Liang, L. Lang, S. Xiao, W. Hu, and H. Deng, “Molecular dynamics simulations of the characteristics of Mo/Ti interfaces,” Computational Materials Science. 2018. link Times cited: 21 USED (low confidence) X.-yan Li et al., “Principal physical parameters characterizing the interactions between irradiation-induced point defects and several tilt symmetric grain boundaries in Fe, Mo and W,” Journal of Nuclear Materials. 2014. link Times cited: 29 USED (low confidence) D. Seif and N. Ghoniem, “Dislocation Bias Calculations in Metals Using a Combined Finite-Element Rate-Theory Approach.” 2013. link Times cited: 2 USED (low confidence) N. Juslin and B. Wirth, “Interatomic potentials for simulation of He bubble formation in W,” Journal of Nuclear Materials. 2013. link Times cited: 231 USED (low confidence) B. Ye, D. Yun, Z. Insepov, and J. Rest, “Multi-Scale Modeling of Interstitial Dislocation Loop Growth in Irradiated Materials,” MRS Proceedings. 2012. link Times cited: 1 USED (low confidence) X.-C. Li, X. Shu, Y. Liu, F. Gao, and G. Lu, “Modified analytical interatomic potential for a W–H system with defects,” Journal of Nuclear Materials. 2011. link Times cited: 100 USED (low confidence) S. Nakagawa, “Characterising Nanoscale Crystal Perfection by Crystal Mapping.” 2009. link Times cited: 1 NOT USED (low confidence) A. Forslund, J. H. Jung, P. Srinivasan, and B. Grabowski, “Thermodynamic properties on the homologous temperature scale from direct upsampling: Understanding electron-vibration coupling and thermal vacancies in bcc refractory metals,” Physical Review B. 2023. link Times cited: 2 Abstract: We have calculated thermodynamic properties of four bcc refr… read moreAbstract: We have calculated thermodynamic properties of four bcc refractory elements—V, Ta, Mo, and W—up to the melting point with full density-functional-theory accuracy, using the recently developed direct-upsampling method [J. H. Jung etal. , npj Comput. Mater. 9 , 3 (2023)]. The direct-upsampling methodology takes full account of explicit anharmonic vibrations and electron-vibration coupling very efficiently using machine-learning potentials. We have thus been able to compute highly converged free-energy surfaces for the PBE exchange-correlation functional, from which accurate temperature dependencies of various thermodynamic properties such as the heat capacity, thermal expansion coefficient, and bulk modulus are accessible. For all four elements, the electronic contribution is large, including a strong coupling with the thermal vibrations. The atomic forces in W are even affected by the temperature-consistent Fermi broadening, which alters the free energy by around 3 meV / atom at the melting point. Trends within group V and group VI refractory elements are observed and explained by qualitative differences in the electronic density of states. We also provide an estimate of the Gibbs energies of vacancy formation and the vacancy contribution to the thermodynamics. Lastly and most importantly, our results are analyzed in terms of the homologous temperature scale relative to theoretically predicted melting points (for the PBE functional). The homologous temperature dependencies show a remarkable agreement with experiments and reveal the predictive power of self-consistently determined ab initio thermodynamic properties. DOI: 10.1103 read less NOT USED (low confidence) S. Lyu and Y. Chen, “Point defect properties of the VCrMnFe0.33 multi-principal alloy from first-principles calculations,” Materials Today Communications. 2022. link Times cited: 1 NOT USED (low confidence) Y. Zhang, Y. Osetsky, and W. J. Weber, “Tunable Chemical Disorder in Concentrated Alloys: Defect Physics and Radiation Performance.,” Chemical reviews. 2021. link Times cited: 35 Abstract: The development of advanced structural alloys with performan… read moreAbstract: The development of advanced structural alloys with performance meeting the requirements of extreme environments in nuclear reactors has been long pursued. In the long history of alloy development, the search for metallic alloys with improved radiation tolerance or increased structural strength has relied on either incorporating alloying elements at low concentrations to synthesize so-called dilute alloys or incorporating nanoscale features to mitigate defects. In contrast to traditional approaches, recent success in synthesizing multicomponent concentrated solid-solution alloys (CSAs), including medium-entropy and high-entropy alloys, has vastly expanded the compositional space for new alloy discovery. Their wide variety of elemental diversity enables tunable chemical disorder and sets CSAs apart from traditional dilute alloys. The tunable electronic structure critically lowers the effectiveness of energy dissipation via the electronic subsystem. The tunable chemical complexity also modifies the scattering mechanisms in the atomic subsystem that control energy transport through phonons. The level of chemical disorder depends substantively on the specific alloying elements, rather than the number of alloying elements, as the disorder does not monotonically increase with a higher number of alloying elements. To go beyond our knowledge based on conventional alloys and take advantage of property enhancement by tuning chemical disorder, this review highlights synergistic effects involving valence electrons and atomic-level and nanoscale inhomogeneity in CSAs composed of multiple transition metals. Understanding of the energy dissipation pathways, deformation tolerance, and structural stability of CSAs can proceed by exploiting the equilibrium and non-equilibrium defect processes at the electronic and atomic levels, with or without microstructural inhomogeneities at multiple length scales. Knowledge of tunable chemical disorder in CSAs may advance the understanding of the substantial modifications in element-specific alloy properties that effectively mitigate radiation damage and control a material's response in extreme environments, as well as overcome strength-ductility trade-offs and provide overarching design strategies for structural alloys. read less NOT USED (low confidence) M. Gilbert et al., “Perspectives on multiscale modelling and experiments to accelerate materials development for fusion,” Journal of Nuclear Materials. 2021. link Times cited: 33 NOT USED (low confidence) Y. Yoshida, “Mössbauer Spectroscopic Studies on Atomic Diffusion in Materials.” 2021. link Times cited: 2 NOT USED (low confidence) X.-T. Li, X. Tang, Y. Fan, and Y. Guo, “The interstitial emission mechanism in a vanadium-based alloy,” Journal of Nuclear Materials. 2020. link Times cited: 9 NOT USED (low confidence) S. Rao, C. Woodward, B. Akdim, and O. Senkov, “A model for interstitial solid solution strengthening of body centered cubic metals,” Materialia. 2020. link Times cited: 22 NOT USED (low confidence) V. Tikare, R. Devanathan, and M. Caturla, “List of Authors,” 2019 Panhellenic Conference on Electronics & Telecommunications (PACET). 2019. link Times cited: 0 NOT USED (low confidence) D. Sangiovanni et al., “Superioniclike Diffusion in an Elemental Crystal: bcc Titanium.,” Physical review letters. 2019. link Times cited: 23 Abstract: Recent theoretical investigations [A. B. Belonoshko et al. N… read moreAbstract: Recent theoretical investigations [A. B. Belonoshko et al. Nat. Geosci. 10, 312 (2017)1752-089410.1038/ngeo2892] revealed the occurrence of the concerted migration of several atoms in bcc Fe at inner-core temperatures and pressures. Here, we combine first-principles and semiempirical atomistic simulations to show that a diffusion mechanism analogous to the one predicted for bcc iron at extreme conditions is also operative and of relevance for the high-temperature bcc phase of pure Ti at ambient pressure. The mechanism entails a rapid collective movement of numerous (from two to dozens) neighbors along tangled closed-loop paths in defect-free crystal regions. We argue that this phenomenon closely resembles the diffusion behavior of superionics and liquid metals. Furthermore, we suggest that concerted migration is the atomistic manifestation of vanishingly small ω-mode phonon frequencies previously detected via neutron scattering and the mechanism underlying anomalously large and markedly non-Arrhenius self-diffusivities characteristic of bcc Ti. read less NOT USED (low confidence) T. Wells, A. Horsfield, W. Foulkes, and S. Dudarev, “The microscopic Einstein-de Haas effect.,” The Journal of chemical physics. 2019. link Times cited: 2 Abstract: The Einstein-de Haas (EdH) effect, where the spin angular mo… read moreAbstract: The Einstein-de Haas (EdH) effect, where the spin angular momentum of electrons is transferred to the mechanical angular momentum of atoms, was established experimentally in 1915. While a semiclassical explanation of the effect exists, modern electronic structure methods have not yet been applied to model the phenomenon. In this paper, we investigate its microscopic origins by means of a noncollinear tight-binding model of an O2 dimer, which includes the effects of spin-orbit coupling, coupling to an external magnetic field, and vector Stoner exchange. By varying an external magnetic field in the presence of spin-orbit coupling, a torque can be generated on the dimer, validating the presence of the EdH effect. The avoided energy level crossings and the rate of change of magnetic field determine the evolution of the spin. We also find that the torque exerted on the nuclei by the electrons in a time-varying B field is not only due to the EdH effect. The other contributions arise from field-induced changes in the electronic orbital angular momentum and from the direct action of the Faraday electric field associated with the time-varying magnetic field. read less NOT USED (low confidence) F. Hofmann, M. Short, and C. Dennett, “Transient grating spectroscopy: An ultrarapid, nondestructive materials evaluation technique,” MRS Bulletin. 2019. link Times cited: 35 Abstract: Structure–property relationships are the foundation of mater… read moreAbstract: Structure–property relationships are the foundation of materials science and are essential for predicting material response to driving forces, managing in-service material degradation, and engineering materials for optimal performance. Elastic, thermal, and acoustic properties provide a convenient gateway to directly or indirectly probe materials structure across multiple length scales. This article will review how using the laser-induced transient grating spectroscopy (TGS) technique, which uses a transient diffraction grating to generate surface acoustic waves and temperature gratings on a material surface, nondestructively reveals the material’s elasticity, thermal diffusivity, and energy dissipation on the sub-microsecond time scale, within a tunable subsurface depth. This technique has already been applied to many challenging problems in materials characterization, from analysis of radiation damage, to colloidal crystals, to phonon-mediated thermal transport in nanostructured systems, to crystal orientation and lattice parameter determination. Examples of these applications, as well as inferring aspects of microstructural evolution, illustrate the wide potential reach of TGS to solve old materials challenges and to uncover new science. We conclude by looking ahead at the tremendous potential of TGS for materials discovery and optimization when applied in situ to dynamically evolving systems. read less NOT USED (low confidence) B. V. D. Meer, R. V. Damme, M. Dijkstra, F. Smallenburg, and L. Filion, “Revealing a Vacancy Analog of the Crowdion Interstitial in Simple Cubic Crystals.,” Physical review letters. 2018. link Times cited: 11 Abstract: Vacancies in simple cubic crystals of hard cubes are known t… read moreAbstract: Vacancies in simple cubic crystals of hard cubes are known to delocalize over one-dimensional chains of several lattice sites. Here, we use computer simulations to examine the structure and dynamics of vacancies in simple cubic crystals formed by hard cubes, right rhombic prisms (slanted cubes), truncated cubes, and particles interacting via a soft isotropic pair potential. We show that these vacancies form a vacancy analog of the crowdion interstitial, generating a strain field which follows a soliton solution of the sine-Gordon equation, and diffusing via a persistent random walk. Surprisingly, we find that the structure of these "voidions" is not significantly affected by changes in density, vacancy concentration, and even particle interaction. We explain this structure quantitatively using a one-dimensional model that includes the free-energy barrier particles have to overcome to slide between lattice sites and the effective pair interaction along this line. We argue that voidions are a robust phenomenon in systems of repulsive particles forming simple cubic crystals. read less NOT USED (low confidence) T. Zou, P. Zhang, J. Zhao, P. Zheng, and J. Chen, “First principles study of vacancy-solute complexes in vanadium,” Journal of Alloys and Compounds. 2018. link Times cited: 17 NOT USED (low confidence) D. Mason, A. Sand, X. Yi, and S. Dudarev, “Direct observation of the spatial distribution of primary cascade damage in tungsten,” Acta Materialia. 2018. link Times cited: 31 NOT USED (low confidence) C. González, B. Biel, and Y. Dappe, “Adsorption of small inorganic molecules on a defective MoS2 monolayer.,” Physical chemistry chemical physics : PCCP. 2017. link Times cited: 54 Abstract: We present a theoretical study of molecular adsorption on de… read moreAbstract: We present a theoretical study of molecular adsorption on defects on a MoS2 monolayer. Based on Density Functional Theory, our calculations confirm that small inorganic molecules, such as CO2, CO, H2O, NO, NO2, H2 and N2, remain bonded to the pristine monolayer through weak van der Waals interactions, suggesting that the molecules may easily diffuse over the clean monolayer. On the other hand, the introduction of defects can lead to three different situations, depending on the defect and the molecule considered: physisorption, chemical (strong) bonding to the metallic defects, namely the Mo substitutional atoms on the S vacancies, and dissociation, that can take place spontaneously at 0 K in some specific cases or by the effect of thermal agitation in molecules such as CO2 or NO2 on the S vacancy. Our energetic and electronic analyses provide an explanation to such bonding possibilities, showing that in the low interacting situations, the molecules tend to adopt a planar configuration parallel to the monolayer, while a molecular rotation is favored in order to facilitate the bond formation on the reactive sites. Finally, the ab initio based Scanning Tunneling Microscopy (STM) simulations show the fingerprint of each molecule adsorbed on the most reactive site. This work opens the way to the possibility of tuning the catalytic properties of MoS2 by controlling the creation of specific defects in the MoS2 monolayer. read less NOT USED (low confidence) D. Seif and N. Ghoniem, “A stochastic differential equations approach for the description of helium bubble size distributions in irradiated metals,” Journal of Nuclear Materials. 2014. link Times cited: 1 NOT USED (low confidence) S. Dudarev, “Density Functional Theory Models for Radiation Damage,” Annual Review of Materials Research. 2013. link Times cited: 79 Abstract: Density functional theory models developed over the past dec… read moreAbstract: Density functional theory models developed over the past decade provide unique information about the structure of nanoscale defects produced by irradiation and about the nature of short-range interaction between radia- tion defects, clustering of defects, and their migration pathways. These ab initio models, involving no experimental input parameters, appear to be as quantitatively accurate and informative as the most advanced experimental techniques developed for the observation of radiation damage phenomena. Density functional theory models have effectively created a new paradigm for the scientific investigation and assessment of radiation damage effects, offering new insight into the origin of temperature- and dose-dependent response of materials to irradiation, a problem of pivotal significance for applications. read less NOT USED (low confidence) D. Duffy, “Energy Generation: Nuclear Energy.” 2013. link Times cited: 0 NOT USED (low confidence) D. N. Manh, M. Muzyk, K. Kurzydłowski, N. Baluc, M. Rieth, and S. Dudarev, “First-Principles Modeling of Tungsten-Based Alloys for Fusion Power Plant Applications,” Key Engineering Materials. 2011. link Times cited: 14 Abstract: We describe a comprehensive ab initio investigation of phase… read moreAbstract: We describe a comprehensive ab initio investigation of phase stability and mechanical properties of W-Ta and W-V alloys, which are candidate materials for fusion power plant applications. The ab initio density functional calculations compare enthalpies of mixing for alternative ordered atomic structures of the alloys, corresponding to the same chemical composition. Combining the ab initio data with large-scale lattice Monte-Carlo simulations, we predict several low-energy intermetallic compounds that are expected to dominate alloy microstructures, and hence the low-temperature phase diagrams, for both alloys. Using the predicted ground-state atomic alloy configurations, we investigate the short-range order, point defect (vacancy and self-interstitial atoms) energies, and thermodynamic and mechanical properties of W alloys as functions of their chemical composition. In particular, we evaluate the anisotropic Young modulus for W-Ta and W-V alloys from ab initio elastic constant calculations, with the objective of comparing the predicted values with experimental micro-cantilever measurements. Also, using the calculated Poisson ratios for binary W alloys, which combine tungsten with more than 40 different alloying elements, we investigate if alloying improves the ductility of tungsten-based materials. read less NOT USED (low confidence) S. Khakshouri and D. Duffy, “Influence of electronic effects on the surface erosion of tungsten,” Physical Review B. 2009. link Times cited: 16 Abstract: Tungsten is a strong contender for a plasma-facing material … read moreAbstract: Tungsten is a strong contender for a plasma-facing material in future fusion power plant designs, and the material of choice for the divertor of ITER, due to its high melting point, thermal conductivity, and resistance to sputtering erosion. Sputtering erosion is a major concern for plasma-facing materials because sputtered atoms could enter the plasma and result in cooling. Atomistic modeling, using molecular dynamics, has previously been successful in identifying fundamental mechanisms of surface damage caused by ion bombardment. The damage has been found to be particularly sensitive to the rate of energy dissipation but energy transport is not well described in classical molecular dynamics simulations of metals. We present a methodology for including a realistic description of electronic energy absorption, transport, and redistribution in molecular dynamics simulations of self sputtering. The results for three different 5 keV self-sputtering events are presented for four distinct thermal transport models. The results demonstrate the sensitivity of surface damage to the model used to describe the electronic thermal transport. read less NOT USED (low confidence) K. Nordlund and S. Dudarev, “Interatomic potentials for simulating radiation damage effects in metals,” Comptes Rendus Physique. 2008. link Times cited: 29 NOT USED (low confidence) S. Giusepponi and M. Celino, “The effects of vacancies in the mechanical properties of tungsten: a first-principles study.,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2015. link Times cited: 10 NOT USED (low confidence) N. Hiroshi, “Defects in Metals.” 2014. link Times cited: 1 NOT USED (low confidence) T. Amino, K. Arakawa, and H. Mori, “Verification of Rate Equation for Recombination between Self-Interstitial Atoms and Vacancies,” Journal of The Japan Institute of Metals. 2011. link Times cited: 0 Abstract: Rate equation (RE) and kinetic Monte Carlo (KMC) simulation … read moreAbstract: Rate equation (RE) and kinetic Monte Carlo (KMC) simulation are widely used to understand the accumulation process of lattice defects upon high-energy particle irradiation. RE is more suitable for the simulation of longer term processes in comparison with KMC simulation. However, the accuracy of the results obtained by RE has not yet been clearly established. In the present study, the accuracy of RE for the reaction between self-interstitial atoms and vacancies in a body-centered cubic lattice is verified using a KMC method. The results show that the accuracy of RE reduces when the spatial correlation among defects is not negligible. read less NOT USED (low confidence) L. Malerba, “Multi-scale modelling of irradiation effects in nuclear power plant materials.” 2010. link Times cited: 3 Abstract: Abstract: This chapter surveys the computer-based multi-scal… read moreAbstract: Abstract: This chapter surveys the computer-based multi-scale modelling approaches currently being used to develop physical models of the effects of radiation on nuclear materials. The focus is on the problem of radiation-induced hardening (and embrittlement) in steels, limited to the scales ranging from the nucleus to the single crystal. First, the multi-scale nature of radiation effects is illustrated, including examples of microstructural and mechanical property changes observed in steels used in nuclear reactors. Then the chapter discusses the fundamental ideas upon which the multi-scale modelling approach is based. Next, an overview of the techniques of use in a multi-scale modelling framework is given, with an example of how these can be integrated. A discussion of the state-of-the-art and other general remarks conclude the chapter. read less NOT USED (high confidence) B. Waters, D. S. Karls, I. Nikiforov, R. Elliott, E. Tadmor, and B. Runnels, “Automated determination of grain boundary energy and potential-dependence using the OpenKIM framework,” Computational Materials Science. 2022. link Times cited: 5 NOT USED (high confidence) R. Brady and E. Samulski, “Thermodynamics of Melting in Colloids and Helium,” Journal of Low Temperature Physics. 2022. link Times cited: 1 NOT USED (high confidence) X. Wang, Y. Wang, L. Zhang, F. Dai, and H. Wang, “A tungsten deep neural-network potential for simulating mechanical property degradation under fusion service environment,” Nuclear Fusion. 2021. link Times cited: 14 Abstract: Tungsten is a promising candidate material in fusion energy … read moreAbstract: Tungsten is a promising candidate material in fusion energy facilities. Molecular dynamics (MD) simulations reveal the atomistic scale mechanisms, so they are crucial for the understanding of the macroscopic property deterioration of tungsten under harsh and complex service environments. The interatomic potential used in the MD simulations is required to accurately describe a wide spectrum of relevant defect properties, which is by far challenging to the existing interatomic potentials. In this paper, we propose a new three-body embedding descriptor and hybridize it into the deep-potential (DP) framework, an end-to-end deep learning interatomic potential model. The potential model for tungsten, named DP-HYB, is trained with a database constructed by the concurrent learning method. The DP-HYB model is able to accurately predict elastic constants, stacking fault energy, the formation energies of free surfaces, and point defects, which are considered in the training dataset. It also accurately evaluates the formation energies of grain boundaries and prismatic loops, the core structure of screw dislocation, the Peierls barrier, and the transition path of the screw dislocation migration, which do not explicitly present in the training dataset. The DP-HYB is a good candidate for the atomistic simulations of tungsten property deterioration, especially those involving the mechanical property degradation under the harsh fusion service environment. read less NOT USED (high confidence) W. Ni et al., “He bubble-driven growth of W fuzz during the interaction between H2/He plasmas and W materials,” Tungsten. 2021. link Times cited: 5 NOT USED (high confidence) T. Suzudo and T. Tsuru, “Inclination of self-interstitial dumbbells in molybdenum and tungsten: A first-principles study,” AIP Advances. 2021. link Times cited: 3 Abstract: Body-centered-cubic (BCC) transition metals are ubiquitous s… read moreAbstract: Body-centered-cubic (BCC) transition metals are ubiquitous structural materials, and their mechanical degradation under irradiation is significantly influenced by the stability and mobility of the lattice defects. In this study, we analyzed the self-interstitial atoms (SIAs) in BCC molybdenum (Mo) and tungsten (W) in comparison with other BCC transition metals utilizing the first-principles method; particularly, we focused on uncommon dumbbells whose direction are inclined from 〈111〉 toward 〈110〉 on the {110} plane. Such a direction is not stable in the group 5 BCC metals (i.e., vanadium, niobium, and tantalum) or in α-iron. Our first-principles relaxation simulations indicated that inclined dumbbells were more energetically favored than common 〈111〉 dumbbells in Mo, while this is not necessarily the case for W. However, a certain degree of lattice strain, such as shear or expansive strain, could make inclined dumbbells more favored also in W, suggesting that the lattice strain can substantially influence the migration barrier of SIAs in these metals because inclined dumbbells generally have a larger migration barrier than 〈111〉 dumbbells. We also elucidated the mechanism of the inclination using the electronic charge density; the charge density map of the perfect crystals suggested that the anti-bonding state of electrons along the 〈111〉 direction is likely to cause the instability of 〈111〉 dumbbells, and the charge density map near dumbbells suggested how 〈111〉 dumbbells are inclined toward the 〈110〉 direction. read less NOT USED (high confidence) G. Nikoulis, J. Byggmästar, J. Kioseoglou, K. Nordlund, and F. Djurabekova, “Machine-learning interatomic potential for W–Mo alloys,” Journal of Physics: Condensed Matter. 2021. link Times cited: 9 Abstract: In this work, we develop a machine-learning interatomic pote… read moreAbstract: In this work, we develop a machine-learning interatomic potential for W x Mo1−x random alloys. The potential is trained using the Gaussian approximation potential framework and density functional theory data produced by the Vienna ab initio simulation package. The potential focuses on properties such as elastic properties, melting, and point defects for the whole range of W x Mo1−x compositions. Moreover, we use all-electron density functional theory data to fit an adjusted Ziegler–Biersack–Littmarck potential for the short-range repulsive interaction. We use the potential to investigate the effect of alloying on the threshold displacement energies and find a significant dependence on the local chemical environment and element of the primary recoiling atom. read less NOT USED (high confidence) M. de Jager, J. D. de Jong, and L. Filion, “Defects in crystals of soft colloidal particles,” Soft Matter. 2021. link Times cited: 0 Abstract: In this paper we use computer simulations to examine point d… read moreAbstract: In this paper we use computer simulations to examine point defects in systems of “soft” colloidal particles including Hertzian spheres, and star polymers. We use Monte Carlo simulations to determine the deformation of the different crystals associated with vacancies and interstitials and use thermodynamic integration to predict the equilibrium concentrations of such defects. We find that the nature of the lattice distortion is mainly determined by the crystal structure and not by the specifics of the interaction potential. We can distinguish one-, two-, and three-dimensional lattice distortions and find that the range of the distortion generally depends on the dimensionality. We find that in both model systems the deformation of the body-centered cubic (BCC) crystal caused by an interstitial is one-dimensional and we show that its structure is well described as a crowdion. Similarly, we show that the one-dimensional deformation of the hexagonal (H) crystal of Hertzian spheres caused by a vacancy can be characterized as a voidion. Interestingly, with the exception of the FCC crystal in the Hertzian sphere model, in all cases we find that the interstitial concentration is higher than the vacancy concentration. Most noteworthy, the concentration of interstitials in the BCC crystals can reach up to 1%. read less NOT USED (high confidence) R. M. Alkemade, M. de Jager, B. van der Meer, F. Smallenburg, and L. Filion, “Point defects in crystals of charged colloids.,” The Journal of chemical physics. 2021. link Times cited: 1 Abstract: Charged colloidal particles-on both the nano and micron scal… read moreAbstract: Charged colloidal particles-on both the nano and micron scales-have been instrumental in enhancing our understanding of both atomic and colloidal crystals. These systems can be straightforwardly realized in the lab and tuned to self-assemble into body-centered-cubic (BCC) and face-centered-cubic (FCC) crystals. While these crystals will always exhibit a finite number of point defects, including vacancies and interstitials-which can dramatically impact their material properties-their existence is usually ignored in scientific studies. Here, we use computer simulations and free-energy calculations to characterize vacancies and interstitials in FCC and BCC crystals of point-Yukawa particles. We show that, in the BCC phase, defects are surprisingly more common than in the FCC phase, and the interstitials manifest as so-called crowdions: an exotic one-dimensional defect proposed to exist in atomic BCC crystals. Our results open the door to directly observe these elusive defects in the lab. read less NOT USED (high confidence) D. Nguyen-Manh, J. Wróbel, M. Klimenkov, M. J. Lloyd, L. Messina, and S. Dudarev, “First-principles model for voids decorated by transmutation solutes: Short-range order effects and application to neutron irradiated tungsten.” 2021. link Times cited: 11 Abstract: Duc Nguyen-Manh, 2, ∗ Jan S. Wróbel, Michael Klimenkov, Matt… read moreAbstract: Duc Nguyen-Manh, 2, ∗ Jan S. Wróbel, Michael Klimenkov, Matthew J. Lloyd, Luca Messina, and Sergei L. Dudarev 2 CCFE, United Kingdom Atomic Energy Authority, Abingdon, Oxfordshire OX14 3DB, United Kingdom Department of Materials, University of Oxford, Parks Road, OX1 3PH, United Kingdom Faculty of Materials Science and Engineering, Warsaw University of Technology, ul. Wo loska 141, 02-507 Warsaw, Poland Karsruhe Institute of Technology, Institute for Applied Materials, 76021 Karsrule, Germany EdF-R&D, Département Matériaux et Mécanique des Composants, Les Renardières, F-77250 Moret sur Loing, France (Dated: February 3, 2021) read less NOT USED (high confidence) U. Bhardwaj, A. Sand, and M. Warrier, “Comparison of SIA defect morphologies from different interatomic potentials for collision cascades in W,” Modelling and Simulation in Materials Science and Engineering. 2020. link Times cited: 4 Abstract: The morphology of defects formed in collision cascades is an… read moreAbstract: The morphology of defects formed in collision cascades is an essential aspect of the subsequent evolution of the microstructure. The morphological composition of a defect decides its stability, interaction, and migration properties. We compare the defect morphologies in the primary radiation damage caused by high energy collision cascades simulated using three different interatomic potentials in W. An automated method to identify morphologies of defects is used. While most defects form 1/2⟨111⟩ dislocation loops, other specific morphologies include ⟨100⟩ dislocation loops, multiple loops clustered together, rings corresponding to C15 configuration and its constituent structures, and a combination of rings and dislocations. The analysis quantifies the distribution of defects among different morphologies and the size distribution of each morphology. We show that the disagreement between predictions of the different potentials regarding defect morphology is much stronger than the differences in predicted defect numbers. read less NOT USED (high confidence) I. Shepelev, D. Bachurin, E. Korznikova, and S. Dmitriev, “Energy exchange in M-crowdion clusters in 2D Morse lattice,” The European Physical Journal B. 2020. link Times cited: 6 NOT USED (high confidence) J. Byggmastar, K. Nordlund, and F. Djurabekova, “Gaussian approximation potentials for body-centered-cubic transition metals,” Physical Review Materials. 2020. link Times cited: 22 Abstract: We develop a set of machine-learning interatomic potentials … read moreAbstract: We develop a set of machine-learning interatomic potentials for elemental V, Nb, Mo, Ta, and W using the Gaussian approximation potential framework. The potentials show good accuracy and transferability for elastic, thermal, liquid, defect, and surface properties. All potentials are augmented with accurate repulsive potentials, making them applicable to radiation damage simulations involving high-energy collisions. We study melting and liquid properties in detail and use the potentials to provide melting curves up to 400 GPa for all five elements. read less NOT USED (high confidence) S. Wen et al., “Effect of transmutation elements Re and Ta on the vacancy formation and dissociation behaviors in W bulk,” Computational Materials Science. 2020. link Times cited: 8 NOT USED (high confidence) T. Ahlgren and K. Heinola, “Improvements to the Sink Strength Theory Used in Multi-Scale Rate Equation Simulations of Defects in Solids,” Materials. 2020. link Times cited: 3 Abstract: The application of mean-field rate theory equations have pro… read moreAbstract: The application of mean-field rate theory equations have proven to be a versatile method in simulating defect dynamics and temporal changes in the microstructure of materials. The reliability and usefulness of the method, however, depends critically on the defect interaction parameters used. In this study, we show that the main interaction parameter, the sink strength, intrinsically depends on the detrapping, or the dissociation process itself. We present a theory on how to determine the appropriate sink strengths. The correct sink strength required for a detrapping defect, is considerably larger than the values commonly used, and thus should not be neglected. read less NOT USED (high confidence) J. Wang, W. Dang, D. Liu, and Z. Guo, “Size effect of He clusters on the interactions with self-interstitial tungsten atoms at different temperatures,” Chinese Physics B. 2020. link Times cited: 3 Abstract: The behaviors of helium cluster and self-interstitial tungst… read moreAbstract: The behaviors of helium cluster and self-interstitial tungsten atom at different temperatures are investigated with molecular dynamics method. The self-interstitial tungsten atoms prefer to form crowdions which tightly binding the helium cluster at low temperature. The crowdion can change its position around the helium cluster through rotating and slipping at medium temperature, which leads to form combined crowdions or dislocation loop locating at one side of helium cluster. The combined crowdions or dislocation loop even separates from helium cluster at high temperature. It is found that the big helium cluster is more stable and it's interaction with crowdions or dislocation loop is more strong. read less NOT USED (high confidence) Y. You et al., “Effects of self-interstitial atom on behaviors of hydrogen and helium in tungsten,” Physica Scripta. 2020. link Times cited: 8 Abstract: Neutron irradiation induces a large number of vacancies and … read moreAbstract: Neutron irradiation induces a large number of vacancies and self-interstitial atoms (SIAs) that interact with hydrogen atoms (H) and degrade the mechanical properties of tungsten (W) in a fusion environment. Vacancies increase free space and trap H atoms, however, the effects of SIAs on trapping H atoms are still unclear since SIAs decrease free space. We therefore perform systematical ab initio calculations to study the interactions of SIAs and SIAs clusters with H atoms in W. Our results suggest that SIA 〈 111 〉 dumbbell makes interstitial H atoms easy to accumulate in W. With accumulation of H atoms near a SIA 〈 111 〉 dumbbell, the binding energy decreases firstly and then levels off at about 0.3 eV. For comparison, the interactions of SIAs and SIAs clusters with helium (He) atoms are considered. It is found that SIAs and SIAs clusters can also act as trapping centers for interstitial He atoms. The combinations of SIAs with H and He hinder the fast movement of SIAs in W to annihilate with vacancies, increasing the concentrations of SIAs and vacancies in grain. SIAs and vacancies provide more sites for trapping H and He atoms and thus increase irradiation damage in W. We therefore suggest reducing retention of H isotopes and He in W to suppress irradiation damage. read less NOT USED (high confidence) J. Chapman, P. Ma, and S. Dudarev, “Effect of non-Heisenberg magnetic interactions on defects in ferromagnetic iron,” Physical Review B. 2020. link Times cited: 4 Abstract: Fundamental flaws in the Heisenberg Hamiltonian are highligh… read moreAbstract: Fundamental flaws in the Heisenberg Hamiltonian are highlighted in the context of its application to BCC Fe, including the particular issues arising when modelling lattice defects. Exchange integrals are evaluated using the magnetic force theorem. The bilinear exchange coupling constants are calculated for all the interacting pairs of atomic magnetic moments in large simulation cells containing defects, enabling a direct mapping of the magnetic energy onto the Heisenberg Hamiltonian and revealing its limitations. We provide a simple procedure for extracting the Landau parameters from DFT calculations, to construct a Heisenberg-Landau Hamiltonian. We quantitatively show how the Landau terms correct the exchange-energy hypersurface, which is essential for the accurate evaluation of energies and migration barriers of defects. read less NOT USED (high confidence) K. Arakawa et al., “Quantum de-trapping and transport of heavy defects in tungsten,” Nature Materials. 2020. link Times cited: 21 NOT USED (high confidence) E. Korznikova, I. Sunagatova, A. Bayazitov, A. Semenov, and S. Dmitirev, “Effect of interatomic potentials on mass transfer by supersonic 2‑crowdions,” Letters on Materials. 2019. link Times cited: 6 Abstract: An interstitial atom placed into a close-packed atomic row i… read moreAbstract: An interstitial atom placed into a close-packed atomic row is called crowdion. Crowdions are very efficient in mass transfer in the crystal lattice since they are highly mobile, soliton-like objects. It has been demonstrated recently that single interstitial atom can move along a close-packed atomic row with a supersonic speed in two different modes, either as a classical 1-crowdion or as a 2-crowdion. The difference is that in the latter case two atoms move with a high speed at the same time, while in the former case only one atom has high speed. It has been shown that the 2-crowdion requires lesser energy to initiate mass transfer and it travels longer distance if it has same energy with the 1-crowdion. It is important to compare the efficiency of mass transfer by 2-crowdions in different materials. Materials have different properties because the interatomic interactions between various atoms are different. In the present study we demonstrate that the most important characteristic of the interatomic potentials, that has effect on the crowdion path length, is the energy of the interatomic bond at the distance between two atoms equal to a half of the equilibrium interatomic distance. This conclusion is justified by the condition of self-focusing propagation of supersonic crowdions, that is the collision velocity of the atoms should not exceed the value when they approach each other closer than half interatomic distance. As an example, mass transfer by 1- and 2-crowdions is considered in two-dimensional triangular lattice with Morse and Born-Mayer potentials. read less NOT USED (high confidence) J. Hou, Y. You, X.-S. Kong, J. Song, and C. Liu, “Accurate Prediction of Nanovoid Structures and Energetics in Bcc Metals,” Computational Materials Science eJournal. 2019. link Times cited: 0 Abstract: Knowledge on structures and energetics of nanovoids is funda… read moreAbstract: Knowledge on structures and energetics of nanovoids is fundamental to understand defect evolution in metals. Yet there remain no reliable methods able to determine essential structural details or to provide accurate assessment of energetics for general nanovoids. In this study, systematic first-principles investigations have been performed to examine stable structures and energetics of nanovoids in bcc metals. A linear relationship between the formation energy and Wigner-Seitz area of nanovoid has been revealed, and it was explicitly demonstrated that stable structures of nanovoids can be precisely determined by minimizing their Wigner-Seitz areas. A new physics-based predictive model has been developed to accurately predict stable structures and energetics for arbitrary-sized nanovoids. This physical model has been well validated by first-principles calculations and recent nanovoid annealing experiments, and shows distinct advantages over the widely used spherical approximation. The present work offers mechanistic insights that crucial for understanding nanovoid formation and evolution, being a critical step towards predictive control and prevention of nanovoid related damage processes in structural metals. read less NOT USED (high confidence) D. Vizoso, C. Deo, and R. Dingreville, “Scaling laws and stability of nano-sized defect clusters in niobium via atomistic simulations and statistical analysis,” Journal of Materials Science. 2019. link Times cited: 4 NOT USED (high confidence) V. Jansson et al., “Tungsten migration energy barriers for surface diffusion: a parameterization for KMC simulations,” Modelling and Simulation in Materials Science and Engineering. 2019. link Times cited: 5 Abstract: We have calculated the migration barriers for surface diffus… read moreAbstract: We have calculated the migration barriers for surface diffusion on tungsten. Our results form a self-sufficient parameterisation for kinetic Monte Carlo simulations of arbitrarily rough atomic tungsten surfaces, as well as nanostructures such as nanotips and nanoclusters. The parameterisation includes first- and second-nearest neighbour atom jump processes, as well as a third-nearest neighbour exchange process. The migration energy barriers of all processes are calculated with the nudged elastic band method. The same attempt frequency for all processes is found sufficient and the value is fitted to molecular dynamics simulations. The model is validated by correctly simulating with kinetic Monte Carlo the energetically favourable W nanocluster shapes, in good agreement with molecular dynamics simulations. read less NOT USED (high confidence) M. Boleininger and S. Dudarev, “Continuum model for the core of a straight mixed dislocation,” Physical Review Materials. 2019. link Times cited: 8 NOT USED (high confidence) J. Byggmastar, A. Hamedani, K. Nordlund, and F. Djurabekova, “Machine-learning interatomic potential for radiation damage and defects in tungsten,” Physical Review B. 2019. link Times cited: 58 Abstract: We introduce a machine-learning interatomic potential for tu… read moreAbstract: We introduce a machine-learning interatomic potential for tungsten using the Gaussian Approximation Potential framework. We specifically focus on properties relevant for simulations of radiation-induced collision cascades and the damage they produce, including a realistic repulsive potential for the short-range many-body cascade dynamics and a good description of the liquid phase. Furthermore, the potential accurately reproduces surface properties and the energetics of vacancy and self-interstitial clusters, which have been long-standing deficiencies of existing potentials. The potential enables molecular dynamics simulations of radiation damage in tungsten with unprecedented accuracy. read less NOT USED (high confidence) A. Fellman, A. Sand, J. Byggmästar, and K. Nordlund, “Radiation damage in tungsten from cascade overlap with voids and vacancy clusters,” Journal of Physics: Condensed Matter. 2019. link Times cited: 28 Abstract: We have performed a systematic molecular dynamics investigat… read moreAbstract: We have performed a systematic molecular dynamics investigation of the effects of overlap of collision cascades in tungsten with pre-existing vacancy-type defects. In particular, we focus on the implications for fusion neutron irradiated tungsten in relation to comparisons with damage production under ion irradiation conditions. We find that overlap of a cascade with a vacancy-type defect decreases the number of new defects with roughly the same functional dependence as previously shown for interstitial clusters. We further find that different mechanisms govern the formation of dislocation loops, resulting in different Burgers vectors, depending on the degree of overlap between the cascade and the defect. Furthermore, we show that overlapping cascades consistently decrease the size of the pre-existing defect. We also observe void-induced cascade splitting at energies far below the subcascade splitting threshold in tungsten. The impact of these mechanisms on radiation damage accumulation and dose rate effects are discussed. read less NOT USED (high confidence) G. Smirnov, G. Smirnov, V. Stegailov, and V. Stegailov, “Formation free energies of point defects and thermal expansion of bcc U and Mo,” Journal of Physics: Condensed Matter. 2019. link Times cited: 9 Abstract: -U is a high temperature body-centred cubic (bcc) phase of u… read moreAbstract: -U is a high temperature body-centred cubic (bcc) phase of uranium which is mechanically unstable at T = 0 K. The point defect properties in pure bcc uranium are not sufficiently well studied. In this work we use classical molecular dynamics simulations with the thermodynamic integration approach to calculate the formation free energies of vacancies and interstitials in bcc uranium and, for comparison, in bcc molybdenum. Contrary to the majority of other metals where the formation free energy is (much) higher for interstitials than for vacancies, our results show that in -uranium interstitials are the dominating type of defects in thermal equilibrium. We discuss the possible implications of this finding in the context of the thermal expansion data for -U that provide a certain supporting evidence. read less NOT USED (high confidence) S.-H. Li, J.-T. Li, and W. Han, “Radiation-Induced Helium Bubbles in Metals,” Materials. 2019. link Times cited: 74 Abstract: Helium (He) bubbles are typical radiation defects in structu… read moreAbstract: Helium (He) bubbles are typical radiation defects in structural materials in nuclear reactors after high dose energetic particle irradiation. In the past decades, extensive studies have been conducted to explore the dynamic evolution of He bubbles under various conditions and to investigate He-induced hardening and embrittlement. In this review, we summarize the current understanding of the behavior of He bubbles in metals; overview the mechanisms of He bubble nucleation, growth, and coarsening; introduce the latest methods of He control by using interfaces in nanocrystalline metals and metallic multilayers; analyze the effects of He bubbles on strength and ductility of metals; and point out some remaining questions related to He bubbles that are crucial for design of advanced radiation-tolerant materials. read less NOT USED (high confidence) J. Chapman, S. Dudarev, and P. Ma, “Dynamics of magnetism in Fe-Cr alloys with Cr clustering,” Physical Review B. 2019. link Times cited: 14 Abstract: The dynamics of magnetic moments in iron-chromium alloys wit… read moreAbstract: The dynamics of magnetic moments in iron-chromium alloys with different levels of Cr clustering show unusual features resulting from the fact that even in a perfect body-centered-cubic structure, magnetic moments exhibit geometric magnetic frustration resembling that of a spin glass. Due to the long range exchange coupling and configuration randomness, magnetic moments of Cr solutes remain noncollinear at all temperatures. To characterize magnetic properties of Fe-Cr alloys, we explore the temperature dependence of magnetization, susceptibility, Curie temperature, and spin-spin correlations with spatial resolution. The static and dynamic magnetic properties are correlated with the microstructure of Fe-Cr, where magnetization and susceptibility are determined by the size of Cr precipitates at nominal Cr concentrations. The Curie temperature is always maximized when the solute concentration of Cr in the $\ensuremath{\alpha}$ phase is close to 5 to 6 at. %, and the susceptibility of Fe atoms is always enhanced at the boundary between a precipitate and solid solution. Interaction between Cr and Fe stimulates magnetic disorder, lowering the effective Curie temperature. Dynamic simulation of evolution of magnetic correlations shows that the spin-spin relaxation time in Fe-Cr alloys is in the 20 to 40 ps range. read less NOT USED (high confidence) Y. Lysogorskiy, T. Hammerschmidt, J. Janssen, J. Neugebauer, and R. Drautz, “Transferability of interatomic potentials for molybdenum and silicon,” Modelling and Simulation in Materials Science and Engineering. 2019. link Times cited: 14 Abstract: Interatomic potentials are widely used in computational mate… read moreAbstract: Interatomic potentials are widely used in computational materials science, in particular for simulations that are too computationally expensive for density functional theory (DFT). Most interatomic potentials have a limited application range and often there is very limited information available regarding their performance for specific simulations. We carried out high-throughput calculations for molybdenum and silicon with DFT and a number of interatomic potentials. We compare the DFT reference calculations and experimental data to the predictions of the interatomic potentials. We focus on a large number of basic materials properties, including the cohesive energy, atomic volume, elastic coefficients, vibrational properties, thermodynamic properties, surface energies and vacancy formation energies, which enables a detailed discussion of the performance of the different potentials. We further analyze correlations between properties as obtained from DFT calculations and how interatomic potentials reproduce these correlations, and suggest a general measure for quantifying the accuracy and transferability of an interatomic potential. From our analysis we do not establish a clearcut ranking of the potentials as each potential has its strengths and weaknesses. It is therefore essential to assess the properties of a potential carefully before application of the potential in a specific simulation. The data presented here will be useful for selecting a potential for simulations of Mo or Si. read less NOT USED (high confidence) D. Mason, D. Nguyen-Manh, M. Marinica, R. Alexander, A. Sand, and S. Dudarev, “Relaxation volumes of microscopic and mesoscopic irradiation-induced defects in tungsten,” Journal of Applied Physics. 2018. link Times cited: 32 Abstract: The low-energy structures of irradiation-induced defects in … read moreAbstract: The low-energy structures of irradiation-induced defects in materials have been studied extensively over several decades, as these determine the available modes by which a defect can diffuse or relax, and how the microstructure of an irradiated material evolves as a function of temperature and time. Consequently, many studies concern the relative energies of possible defect structures, and empirical potentials are commonly fitted to or evaluated with respect to these. But recently [S. L. Dudarev et al., Nucl. Fusion 58, 126002 (2018)], we have shown that other parameters of defects not directly related to defect energies, namely, their elastic dipole tensors and relaxation volumes, determine the stresses, strains, and swelling of reactor components under irradiation. These elastic properties of defects have received comparatively little attention. In this study, we compute relaxation volumes of irradiation-induced defects in tungsten using empirical potentials and compare to density functional theory results. Different empirical potentials give different results, but some clear potential-independent trends can be identified. We show that the relaxation volume of a small defect cluster can be predicted to within 10% from its point-defect count. For larger defect clusters, we provide empirical fits as a function of defect cluster size. We demonstrate that the relaxation volume associated with a single primary-damage cascade can be estimated from the primary knock-on atom energy. We conclude that while annihilation of defects invariably reduces the total relaxation volume of the cascade debris, there is still no conclusive verdict about whether coalescence of defects reduces or increases the total relaxation volume. read less NOT USED (high confidence) E. Korznikova, I. Shepelev, A. Chetverikov, S. V. Dmitriev, S. Fomin, and K. Zhou, “Dynamics and Stability of Subsonic Crowdion Clusters in 2D Morse Crystal,” Journal of Experimental and Theoretical Physics. 2018. link Times cited: 15 NOT USED (high confidence) E. Igumbor, E. Omotoso, A. Khaleed, and B. Taleatu, “Ab initio study of transition metals impurities and stability of complexes in germanium (Ge),” Ife Journal of Science. 2018. link Times cited: 0 Abstract: By means of density functional theory, we present results of… read moreAbstract: By means of density functional theory, we present results of an ab initio calculation of vacancy-interstitial complexes (T Ge -V nGe I T , for n = 1, 2, 3 and T: Cr, Mo, W, Mn and Fe) in Ge. The projector-augmented wave pseudo-potential within the generalized gradient approximation was used for all calculations. Structural properties and formation energies of the T Ge -V nGe I T for the neutral charge state were obtained. Our results show that under equilibrium conditions, vacancy-interstitial complex T Ge -V nGe I T formed with formation energies not higher than –1.00 eV. The formation energy result showed that the T Ge -V nGe I T is energetically more favourable for n = 1 and 2 than n = 3. The stabilities of the vacancy-interstitial complexes were obtained from their binding energies. For all T, the binding energies of the T Ge -V Ge I T are stable. For the T Ge -V 2Ge I T and T Ge -V 3Ge I T , their binding energies lie between 1.79 and 6.10 eV and defect complexes are stable. Keywords: Density functional theory, vacancy-interstitial, formation energy, impurities read less NOT USED (high confidence) S. Fitzgerald, “Structure and dynamics of crowdion defects in bcc metals,” Journal of Micromechanics and Molecular Physics. 2018. link Times cited: 9 Abstract: Crowdion defects are produced in body-centered-cubic metals … read moreAbstract: Crowdion defects are produced in body-centered-cubic metals under irradiation. Their structure and diffusive dynamics play a governing role in microstructural evolution, and hence the mechanical properties of nuclear materials. In this paper, we apply the analytical Frenkel-Kontorova model to crowdions and clusters thereof (prismatic dislocation loops) and show that the Peierls potential in which these defects diffuse is remarkably small (in the micro eV range as compared to the eV range for other defects). We also develop a coarse-grained statistical methodology for simulating these fast-diffusing objects in the context of object kinetic Monte Carlo, which is less vulnerable to the low barrier problem than naïve stochastic simulation. read less NOT USED (high confidence) W. Setyawan, N. Gao, and R. Kurtz, “A tungsten-rhenium interatomic potential for point defect studies,” Journal of Applied Physics. 2018. link Times cited: 22 Abstract: A tungsten-rhenium (W-Re) classical interatomic potential is… read moreAbstract: A tungsten-rhenium (W-Re) classical interatomic potential is developed within the embedded atom method interaction framework. A force-matching method is employed to fit the potential to ab initio forces, energies, and stresses. Simulated annealing is combined with the conjugate gradient technique to search for an optimum potential from over 1000 initial trial sets. The potential is designed for studying point defects in W-Re systems. It gives good predictions of the formation energies of Re defects in W and the binding energies of W self-interstitial clusters with Re. The potential is further evaluated for describing the formation energy of structures in the σ and χ intermetallic phases. The predicted convex-hulls of formation energy are in excellent agreement with ab initio data. In pure Re, the potential can reproduce the formation energies of vacancies and self-interstitial defects sufficiently accurately and gives the correct ground state self-interstitial configuration. Furthermore, by including liquid structures in the fit, the potential yields a Re melting temperature (3130 K) that is close to the experimental value (3459 K).A tungsten-rhenium (W-Re) classical interatomic potential is developed within the embedded atom method interaction framework. A force-matching method is employed to fit the potential to ab initio forces, energies, and stresses. Simulated annealing is combined with the conjugate gradient technique to search for an optimum potential from over 1000 initial trial sets. The potential is designed for studying point defects in W-Re systems. It gives good predictions of the formation energies of Re defects in W and the binding energies of W self-interstitial clusters with Re. The potential is further evaluated for describing the formation energy of structures in the σ and χ intermetallic phases. The predicted convex-hulls of formation energy are in excellent agreement with ab initio data. In pure Re, the potential can reproduce the formation energies of vacancies and self-interstitial defects sufficiently accurately and gives the correct ground state self-interstitial configuration. Furthermore, by including liqu... read less NOT USED (high confidence) A. M. Marjaneh et al., “Mass transfer in the Frenkel-Kontorova chain initiated by molecule impact.,” Physical review. E. 2018. link Times cited: 23 Abstract: The Frenkel-Kontorova chain with a free end is used to study… read moreAbstract: The Frenkel-Kontorova chain with a free end is used to study initiation and propagation of crowdions (antikinks) caused by impact of a molecule consisting of K atoms. It is found that molecules with 1 read less NOT USED (high confidence) W. Unn-Toc, M. Marinica, and T. Jourdan, “Helium–vacancy interactions in vanadium and tantalum,” Computational Materials Science. 2018. link Times cited: 5 NOT USED (high confidence) R. Sundeev, A. Glezer, and A. Shalimova, “Phase Transformations «Amorphization ↔ Crystallization» In Metallic Materials Induced by Severe Plastic Deformation,” REVIEWS ON ADVANCED MATERIALS SCIENCE. 2018. link Times cited: 9 Abstract: In this review we are considered systematically the phenomen… read moreAbstract: In this review we are considered systematically the phenomenon of deformation-induced phase transformations from crystalline intermetallic compounds and complex phases to amorphous state and vice versa phase transformations from amorphous state to crystalline one upon severe plastic deformation at different temperatures. The nature and structural features of these transitions essentially for high pressure torsion deformation are analyzed in the frame of basic principles of nonequilibrium thermodynamics. The effects of phase cycling and a stationary amorphous - nanocrystalline state formation at significant deformations is discussed in details. read less NOT USED (high confidence) V. Sagaradze et al., “Low Temperature Diffusion Transformations in Fe–Ni–Ti Alloys During Deformation and Irradiation,” Metals and Materials International. 2018. link Times cited: 5 NOT USED (high confidence) D. Thompson, E. Tarleton, S. Roberts, and S. Fitzgerald, “Interstitial-mediated dislocation climb and the weakening of particle-reinforced alloys under irradiation,” Physical Review Materials. 2018. link Times cited: 11 Abstract: Dislocations can climb out of their glide plane by absorbing… read moreAbstract: Dislocations can climb out of their glide plane by absorbing (or emitting) point defects [vacancies and self-interstitial atoms (SIAs)]. In contrast with conservative glide motion, climb relies on the point defects' thermal diffusion and hence operates on much longer timescales, leading to some forms of creep. While equilibrium point defect concentrations allow dislocations to climb to relieve nonglide stresses, point defect supersaturations also lead to osmotic forces, driving dislocation motion even in the absence of external stresses. Self-interstitial atoms typically have significantly higher formation energies than vacancies, so their contribution to climb is usually ignored. However, under irradiation conditions, both types of defect are athermally created in equal numbers. In this paper, we use simple thermodynamic arguments to show that the contribution of interstitials cannot be neglected in irradiated materials and that the osmotic force they induce on dislocations is many orders of magnitude larger than that caused by vacancies. This explains why the prismatic dislocation loops observed by in situ transmission electron microscope irradiations are more often of interstitial rather than vacancy character. Using discrete dislocation dynamics simulations, we investigate the effect on dislocation-obstacle interactions and find reductions in the depinning time of many orders of magnitude. This has important consequences for the strength of particle-reinforced alloys under irradiation. read less NOT USED (high confidence) T. Ahlgren and L. Bukonte, “Sink strength simulations using the Monte Carlo method: Applied to spherical traps,” Journal of Nuclear Materials. 2017. link Times cited: 9 NOT USED (high confidence) N. Castin, A. Bakaev, G. Bonny, A. Sand, L. Malerba, and D. Terentyev, “On the onset of void swelling in pure tungsten under neutron irradiation: An object kinetic Monte Carlo approach,” Journal of Nuclear Materials. 2017. link Times cited: 56 NOT USED (high confidence) T. Swinburne, P. Ma, and S. Dudarev, “Low temperature diffusivity of self-interstitial defects in tungsten,” New Journal of Physics. 2017. link Times cited: 39 Abstract: The low temperature diffusivity of nanoscale crystal defects… read moreAbstract: The low temperature diffusivity of nanoscale crystal defects, where quantum mechanical fluctuations are known to play a crucial role, are essential to interpret observations of irradiated microstructures conducted at cryogenic temperatures. Using density functional theory calculations, quantum heat bath molecular dynamics and open quantum systems theory, we evaluate the low temperature diffusivity of self-interstitial atom clusters in tungsten valid down to temperatures of 1 K. Due to an exceptionally low defect migration barrier, our results show that interstitial defects exhibit very high diffusivity of order 10 3 μ m 2 s − 1 over the entire range of temperatures investigated. read less NOT USED (high confidence) L. Zhang, L. Chen, H. Zhang, Y. Yang, and X. Liu, “Recognition of 5‐fluorouracil by thermosensitive magnetic surface molecularly imprinted microspheres designed using a computational approach,” Journal of Applied Polymer Science. 2017. link Times cited: 11 Abstract: Thermosensitive magnetic surface molecularly imprinted polym… read moreAbstract: Thermosensitive magnetic surface molecularly imprinted polymer microspheres based on thermosensitive monomer n-isopropylacrylamide (NIPAM) are applied for the recognition of 5-fluorouracil (5-FU). A computational analysis is used to predict the interaction sites between 5-FU and NIPAM, the stoichiometry of the synthesis procedure, and the affinity of imprinted cavities toward 5-FU. Due to hydrogen bond interactions, a stable complex configuration of 5-FU and NIPAM shows a binding energy of −46.50 kJ/mol confirming the suitability of imprinting 5-FU into thermosensitive polymer network. After optimization, the appropriate stoichiometry of 5-FU to NIPAM is set to 1:4 during the preparation process. The simulated imprinted cavities show affinity toward 5-FU, with a binding energy of −112.24 kJ/mol. A preliminary experimental evaluation for the drug recognition of thermosensitive magnetic surface molecularly imprinted polymer microspheres is made, obtaining an adsorption capacity of 21.72 mg/g at 25 °C. Pseudo-second-order kinetics well describes the adsorption process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45468. read less NOT USED (high confidence) T. Koyanagi et al., “Microstructural evolution of pure tungsten neutron irradiated with a mixed energy spectrum,” Journal of Nuclear Materials. 2017. link Times cited: 85 NOT USED (high confidence) R. Abernethy, “Predicting the performance of tungsten in a fusion environment: a literature review,” Materials Science and Technology. 2017. link Times cited: 86 Abstract: Tungsten has been proposed for use in the divertor of future… read moreAbstract: Tungsten has been proposed for use in the divertor of future fusion devices. In this environment, it will be exposed to high heat fluxes, neutron damage and hydrogen and helium implantation. This review covers previous experimental and modelling work to establish our ability to predict the performance of tungsten in a fusion environment. Surrogates for high-energy neutrons have been used to predict the change in mechanical properties of tungsten, including fission neutron and self-ion exposure. These studies are critically analysed, with a focus on the difference in results from neutron and ion studies. Further studies to improve our ability to predict the performance of tungsten are proposed as a critical part of the path towards a working fusion reactor. This review was submitted as part of the 2016 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged Video abstract Read the transcript Watch the video on Vimeo read less NOT USED (high confidence) W. Setyawan, G. Nandipati, and R. Kurtz, “Ab initio study of interstitial cluster interaction with Re, Os, and Ta in W,” Journal of Nuclear Materials. 2017. link Times cited: 41 NOT USED (high confidence) P. Ma, S. Dudarev, and C. Woo, “SPILADY: A parallel CPU and GPU code for spin-lattice magnetic molecular dynamics simulations,” Comput. Phys. Commun. 2016. link Times cited: 28 NOT USED (high confidence) G. Huang, N. Juslin, and B. Wirth, “First-principles study of vacancy, interstitial, noble gas atom interstitial and vacancy clusters in bcc-W,” Computational Materials Science. 2016. link Times cited: 52 NOT USED (high confidence) D. Wang 王 et al., “Effect of Strain Field on Threshold Displacement Energy of Tungsten Studied by Molecular Dynamics Simulation,” Chinese Physics Letters. 2016. link Times cited: 11 Abstract: The influence of strain field on defect formation energy and… read moreAbstract: The influence of strain field on defect formation energy and threshold displacement energy (Ed) in body-centered cubic tungsten (W) is studied with molecular dynamics simulation. Two different W potentials (Fikar and Juslin) are compared and the results indicate that the connection distance and selected function linking the short-range and long-range portions of the potentials affect the threshold displacement energy and its direction-specific values. The minimum Ed direction calculated with the Fikar potential is 〈100〉 and with the Juslin potential is 〈111〉. Nevertheless, the most stable self-interstitial configuration is found to be a 〈111〉-crowdion for both the potentials. This stable configuration does not change with the applied strain. Varying the strain from compression to tension increases the vacancy formation energy while decreases the self-interstitial formation energy. The formation energy of a self-interstitial changes more significantly than a vacancy such that Ed decreases with the applied hydrostatic strain from compression to tension. read less NOT USED (high confidence) L. Gharaee, J. Marian, and P. Erhart, “The role of interstitial binding in radiation induced segregation in W-Re alloys,” Journal of Applied Physics. 2016. link Times cited: 36 Abstract: Due to their high strength and advantageous high-temperature… read moreAbstract: Due to their high strength and advantageous high-temperature properties, tungsten-based alloys are being considered as plasma-facing candidate materials in fusion devices. Under neutron irradiation, rhenium, which is produced by nuclear transmutation, has been found to precipitate in elongated precipitates forming thermodynamic intermetallic phases at concentrations well below the solubility limit. Recent measurements have shown that Re precipitation can lead to substantial hardening, which may have a detrimental effect on the fracture toughness of W alloys. This puzzle of sub-solubility precipitation points to the role played by irradiation induced defects, specifically mixed solute-W interstitials. Here, using first-principles calculations based on density functional theory, we study the energetics of mixed interstitial defects in W-Re, W-V, and W-Ti alloys, as well as the heat of mixing for each substitutional solute. We find that mixed interstitials in all systems are strongly attracted to each other with binding energies of -2.4 to -3.2 eV and form interstitial pairs that are aligned along parallel first-neighbor strings. Low barriers for defect translation and rotation enable defect agglomeration and alignment even at moderate temperatures. We propose that these elongated agglomerates of mixed-interstitials may act as precursors for the formation of needle-shaped intermetallic precipitates. This interstitial-based mechanism is not limited to radiation induced segregation and precipitation in W-Re alloys but is also applicable to other body-centered cubic alloys. read less NOT USED (high confidence) X. Yi, M. Jenkins, M. Kirk, Z. Zhou, and S. Roberts, “In-situ TEM studies of 150 keV W+ ion irradiated W and W-alloys: Damage production and microstructural evolution,” Acta Materialia. 2016. link Times cited: 133 NOT USED (high confidence) T. Amino, K. Arakawa, and H. Mori, “Detection of one-dimensional migration of single self-interstitial atoms in tungsten using high-voltage electron microscopy,” Scientific Reports. 2016. link Times cited: 26 NOT USED (high confidence) V. Sagaradze et al., “Deformation-induced dissolution of the intermetallics Ni3Ti and Ni3Al in austenitic steels at cryogenic temperatures,” Philosophical Magazine. 2016. link Times cited: 17 Abstract: An anomalous deformation-induced dissolution of the intermet… read moreAbstract: An anomalous deformation-induced dissolution of the intermetallics Ni3Al and Ni3Ti in the matrix of austenitic Fe–Ni–Al(Ti) alloys has been revealed in experiment at cryogenic temperatures (down to 77 K) under rolling and high pressure torsion. The observed phenomenon is explained as the result of migration of deformation-stipulated interstitial atoms from a particle into the matrix in the stress field of moving dislocations. With increasing the temperature of deformation, the dissolution is replaced by the deformation-induced precipitation of the intermetallics, which is accelerated due to a sufficient amount of point defects in the matrix, gained as well in the course of deformation at lower temperatures. read less NOT USED (high confidence) J. J. Möller and E. Bitzek, “BDA: A novel method for identifying defects in body-centered cubic crystals,” MethodsX. 2016. link Times cited: 17 NOT USED (high confidence) H. Zhang et al., “Stability of concentration-related self-interstitial atoms in fusion material tungsten,” Chinese Physics B. 2016. link Times cited: 3 Abstract: Based on the density functional theory, we calculated the st… read moreAbstract: Based on the density functional theory, we calculated the structures of the two main possible self-interstitial atoms (SIAs) as well as the migration energy of tungsten (W) atoms. It was found that the difference of the 〈110〉 and 〈111〉 formation energies is 0.05–0.3 eV. Further analysis indicated that the stability of SIAs is closely related to the concentration of the defect. When the concentration of the point defect is high, 〈110〉 SIAs are more likely to exist, 〈111〉 SIAs are the opposite. In addition, the vacancy migration probability and self-recovery zones for these SIAs were researched by making a detailed comparison. The calculation provided a new viewpoint about the stability of point defects for self-interstitial configurations and would benefit the understanding of the control mechanism of defect behavior for this novel fusion material. read less NOT USED (high confidence) N. Hu, H. Deng, C. Wang, and W. Hu, “Atomic simulation of helium trapping in displacement cascades,” RSC Advances. 2016. link Times cited: 5 Abstract: A molecular dynamics method is applied to simulate displacem… read moreAbstract: A molecular dynamics method is applied to simulate displacement cascades in He-doped α-Fe and predominant analytical attention is paid to the clustering of He-participating defect clusters to reveal the trapping behaviors of helium atoms in radiation processes. It is found that the radiation temperature, PKA energy and helium concentration play complex roles in defect production. An increase in helium atoms increases the number of defects and the increasing rate is greatly enhanced with the increase in PKA energy and initial radiation temperature. Cascade collisions significantly promote helium trapping through two types of mechanism, thermally activated self-trapping and cascade defect-created capture. Thermally activated self-trapping rather than cascade defect capturing causes helium trapping in displacement cascades. read less NOT USED (high confidence) D. Xu, G. VanCoevering, and B. Wirth, “Defect microstructural equivalence in molybdenum under different irradiation conditions at low temperatures and low doses,” Computational Materials Science. 2016. link Times cited: 9 NOT USED (high confidence) A. Vattré, T. Jourdan, H. Ding, M. Marinica, M. Demkowicz, and M. Demkowicz, “Non-random walk diffusion enhances the sink strength of semicoherent interfaces,” Nature Communications. 2016. link Times cited: 82 NOT USED (high confidence) S. T. Murphy et al., “Dynamical simulations of an electronically induced solid-solid phase transformation in tungsten,” Physical Review B. 2015. link Times cited: 30 Abstract: The rearrangement of a material's electron density duri… read moreAbstract: The rearrangement of a material's electron density during laser irradiation leads to modified nonthermal forces on the atoms that may lead to coherent atomic motions and structural phase transformation on very short time scales. We present ab initio molecular dynamics simulations of a martensitic solid-solid phase transformation in tungsten under conditions of strong electronic excitation. The transformation is ultrafast, taking just over a picosecond, and follows the tetragonal Bain path. To examine whether a solid-solid bcc-fcc phase transformation could occur during laser irradiation, we use two-temperature molecular dynamics (2T-MD) simulations with a specially developed potential dependent on the electronic temperature. Our simulations show that the occurrence of the solid-solid phase transformation is in competition with ultrafast nonthermally assisted melting with the strength of the electron-phonon coupling determining the lifetime of the new solid phase. In tungsten the melting transition is predicted to occur too rapidly for the fcc phase to be detectable during laser irradiation. read less NOT USED (high confidence) D. Kato, H. Iwakiri, Y. Watanabe, K. Morishita, and T. Muroga, “Super-saturated hydrogen effects on radiation damages in tungsten under the high-flux divertor plasma irradiation,” Nuclear Fusion. 2015. link Times cited: 36 Abstract: Tungsten is a prime candidate as the divertor material of th… read moreAbstract: Tungsten is a prime candidate as the divertor material of the ITER and DEMO reactors, which would be exposed to unprecedentedly high-flux plasmas as well as neutrons. For a better characterization of radiation damages in the tungsten under the divertor condition, we examine influences of super-saturated hydrogen on vacancies in the tungsten. The present calculations based on density functional theory (DFT) reveal unusual phenomena predicted at a super-saturated hydrogen concentration: (1) strongly enhanced vacancy concentration with the super-saturated hydrogen concentration is predicted by a thermodynamics model assuming multiple-hydrogen trapping, i.e. hydrogen clusters formation, in the vacancies; and (2) DFT molecular dynamics revealed that hydrogen clusters can prevent a vacancy from recombining with the neighboring crowdion-type self-interstitial-atom. This suggests that neutron damage effects will be increased in the presence of the hydrogen clusters. read less NOT USED (high confidence) G. Nandipati, W. Setyawan, H. Heinisch, K. Roche, R. Kurtz, and B. Wirth, “Displacement cascades and defect annealing in tungsten, Part III: The sensitivity of cascade annealing in tungsten to the values of kinetic parameters,” Journal of Nuclear Materials. 2015. link Times cited: 15 NOT USED (high confidence) L. Niu et al., “Interplay between intrinsic point defects and low-angle grain boundary in bcc tungsten: effects of local stress field,” Journal of Physics: Condensed Matter. 2015. link Times cited: 19 Abstract: We have used molecular statics in conjunction with an embedd… read moreAbstract: We have used molecular statics in conjunction with an embedded atom method to explore the interplay between native point defects (vacancies and self-interstitials (SIAs)) and a low-angle grain boundary (GB) in bcc tungsten. The low-angle GB has biased absorption of SIAs over vacancies. We emphasize the significance of phenomena such as vacancy delocalization and SIA instant absorption around the GB dislocation cores in stabilizing the defect structures. Interstitial loading into the GB can dramatically enhance the interaction strength between the point defects and the GB due to SIA clustering (SIA cloud formation) or SIA vacancy recombination. We propose that the ‘maximum atom displacement’ can complement the ‘vacancy formation energy’ in evaluating unstable vacancy sites. Calculations of point defect migration barriers in the vicinity of GB dislocation cores show that vacancies and SIAs preferentially migrate along the pathways in the planes immediately above and below the core, respectively. read less NOT USED (high confidence) F. Ferroni, X. Yi, K. Arakawa, S. Fitzgerald, P. Edmondson, and S. Roberts, “High temperature annealing of ion irradiated tungsten,” Acta Materialia. 2015. link Times cited: 159 NOT USED (high confidence) D. Ford, P. Zapol, and L. Cooley, “First-principles Study of Carbon and Vacancy Structures in Niobium,” Journal of Physical Chemistry C. 2015. link Times cited: 16 Abstract: The interstitial chemical impurities hydrogen, oxygen, nitro… read moreAbstract: The interstitial chemical impurities hydrogen, oxygen, nitrogen, and carbon are important for niobium metal production and particularly for the optimization of niobium SRF technology. These atoms are present in refined sheets and can be absorbed into niobium during processing treatments, resulting in changes to the residual resistance and the performance of SRF cavities. A first-principles approach is taken to study the properties of carbon in niobium, and the results are compared and contrasted with the properties of the other interstitial impurities. The results indicate that C will likely form precipitates or atmospheres around defects rather than strongly bound complexes with other impurities. On the basis of the analysis of carbon and hydrogen near niobium lattice vacancies and small vacancy chains and clusters, the formation of extended carbon chains and hydrocarbons is not likely to occur. Association of carbon with hydrogen atoms can, however, occur through the strain fields created by interstitia... read less NOT USED (high confidence) C. González, C. González, M. A. Cerdeira, S. L. Palacios, and R. Iglesias, “Reduction of the repulsive interaction as origin of helium trapping inside a monovacancy in BCC metals,” Journal of Materials Science. 2015. link Times cited: 16 NOT USED (high confidence) W. Setyawan, A. P. Selby, N. Juslin, R. Stoller, B. Wirth, and R. Kurtz, “Cascade morphology transition in bcc metals,” Journal of Physics: Condensed Matter. 2014. link Times cited: 44 Abstract: Energetic atom collisions in solids induce shockwaves with c… read moreAbstract: Energetic atom collisions in solids induce shockwaves with complex morphologies. In this paper, we establish the existence of a morphological transition in such cascades. The order parameter of the morphology is defined as the exponent, b, in the defect production curve as a function of cascade energy . Response of different bcc metals can be compared in a consistent energy domain when the energy is normalized by the transition energy, μ, between the high- and the low-energy regime. Using Cr, Fe, Mo and W data, an empirical formula of μ as a function of displacement threshold energy, Ed, is presented for bcc metals. read less NOT USED (high confidence) A. Barashev, H. Xu, and R. Stoller, “The behavior of small helium clusters near free surfaces in tungsten,” Journal of Nuclear Materials. 2014. link Times cited: 32 NOT USED (high confidence) G. Bonny, P. Grigorev, P. Grigorev, and D. Terentyev, “On the binding of nanometric hydrogen–helium clusters in tungsten,” Journal of Physics: Condensed Matter. 2014. link Times cited: 75 Abstract: In this work we developed an embedded atom method potential … read moreAbstract: In this work we developed an embedded atom method potential for large scale atomistic simulations in the ternary tungsten–hydrogen–helium (W–H–He) system, focusing on applications in the fusion research domain. Following available ab initio data, the potential reproduces key interactions between H, He and point defects in W and utilizes the most recent potential for matrix W. The potential is applied to assess the thermal stability of various H–He complexes of sizes too large for ab initio techniques. The results show that the dissociation of H–He clusters stabilized by vacancies will occur primarily by emission of hydrogen atoms and then by break-up of V–He complexes, indicating that H–He interaction does influence the release of hydrogen. read less NOT USED (high confidence) J. Rest, Z. Insepov, B. Ye, and D. Yun, “A multiscale method for the analysis of defect behavior in Mo during electron irradiation,” Computational Materials Science. 2014. link Times cited: 7 NOT USED (high confidence) W. Zhou, C. G. Zhang, Y. Li, and Z. Zeng, “Transport, Dissociation and Rotation of Small Self-interstitial Atom Clusters in Tungsten,” Journal of Nuclear Materials. 2014. link Times cited: 28 NOT USED (high confidence) D. Mason, “Incorporating non-adiabatic effects in embedded atom potentials for radiation damage cascade simulations,” Journal of Physics: Condensed Matter. 2014. link Times cited: 22 Abstract: In radiation damage cascade displacement spikes ions and ele… read moreAbstract: In radiation damage cascade displacement spikes ions and electrons can reach very high temperatures and be out of thermal equilibrium. Correct modelling of cascades with molecular dynamics should allow for the non-adiabatic exchange of energy between ions and electrons using a consistent model for the electronic stopping, electronic temperature rise, and thermal conduction by the electrons. We present a scheme for correcting embedded atom potentials for these non-adiabatic properties at the level of the second-moment approximation, and parameterize for the bcc transition metals above the Debye temperature. We use here the Finnis–Sinclair and Derlet–Nguyen–Manh–Dudarev potentials as models for the bonding, but the corrections derived from them can be applied to any suitable empirical potential. We show with two-temperature MD simulations that computing the electronic thermal conductivity during the cascade evolution has a significant impact on the heat exchange between ions and electrons. read less NOT USED (high confidence) C. González and R. Iglesias, “Migration mechanisms of helium in copper and tungsten,” Journal of Materials Science. 2014. link Times cited: 37 NOT USED (high confidence) T. Faney and B. Wirth, “Spatially dependent cluster dynamics modeling of microstructure evolution in low energy helium irradiated tungsten,” Modelling and Simulation in Materials Science and Engineering. 2014. link Times cited: 44 Abstract: In fusion reactors, plasma facing components (PFC) and in pa… read moreAbstract: In fusion reactors, plasma facing components (PFC) and in particular the divertor will be irradiated with high fluxes of low energy (∼100 eV) helium and hydrogen ions. Tungsten is one of the leading candidate divertor materials for ITER and DEMO fusion reactors. However, the behavior of tungsten under high dose, coupled helium/hydrogen exposure remains to be fully understood. The PFC response and performance changes are intimately related to microstructural changes, such as the formation of point defect clusters, helium and hydrogen bubbles or dislocation loops. Computational materials modeling has been used to investigate the mechanisms controlling microstructural evolution in tungsten following high dose, high temperature helium exposure. The aim of this study is to understand and predict helium implantation, primary defect production and defect diffusion, helium-defect clustering and interactions below a tungsten surface exposed to low energy helium irradiation. The important defects include interstitial clusters, vacancy clusters, helium interstitials and helium-vacancy clusters. We report results from a one-dimensional, spatially dependent cluster dynamics model based on the continuum reaction–diffusion rate theory to describe the evolution in space and time of all these defects. The key parameter inputs to the model (diffusion coefficients, migration and binding energies, initial defect production) are determined from a combination of atomistic materials modeling and available experimental data. read less NOT USED (high confidence) G.-H. Lu, H.-B. Zhou, and C. S. Becquart, “A review of modelling and simulation of hydrogen behaviour in tungsten at different scales,” Nuclear Fusion. 2014. link Times cited: 1 Abstract: Tungsten (W) is considered to be one of the most promising p… read moreAbstract: Tungsten (W) is considered to be one of the most promising plasma-facing materials (PFMs) for next-step fusion energy systems. However, as a PFM, W will be subjected to extremely high fluxes of low-energy hydrogen (H) isotopes, leading to retention of H isotopes and blistering in W, which will degrade the thermal and mechanical properties of W. Modelling and simulation are indispensable to understand the behaviour of H isotopes including dissolution, diffusion, accumulation and bubble formation, which can contribute directly to the design, preparation and application of W as a PFM under a fusion environment. This paper reviews the recent findings regarding the behaviour of H in W obtained via modelling and simulation at different scales. read less NOT USED (high confidence) G. Bonny, D. Terentyev, A. Bakaev, P. Grigorev, and D. V. Neck, “Many-body central force potentials for tungsten,” Modelling and Simulation in Materials Science and Engineering. 2014. link Times cited: 79 Abstract: Tungsten and tungsten-based alloys are the primary candidate… read moreAbstract: Tungsten and tungsten-based alloys are the primary candidate materials for plasma facing components in fusion reactors. The exposure to high-energy radiation, however, severely degrades the performance and lifetime limits of the in-vessel components. In an effort to better understand the mechanisms driving the materials' degradation at the atomic level, large-scale atomistic simulations are performed to complement experimental investigations. At the core of such simulations lies the interatomic potential, on which all subsequent results hinge. In this work we review 19 central force many-body potentials and benchmark their performance against experiments and density functional theory (DFT) calculations. As basic features we consider the relative lattice stability, elastic constants and point-defect properties. In addition, we also investigate extended lattice defects, namely: free surfaces, symmetric tilt grain boundaries, the 1/2〈1 1 1〉{1 1 0} and 1/2〈1 1 1〉 {1 1 2} stacking fault energy profiles and the 1/2〈1 1 1〉 screw dislocation core. We also provide the Peierls stress for the 1/2〈1 1 1〉 edge and screw dislocations as well as the glide path of the latter at zero Kelvin. The presented results serve as an initial guide and reference list for both the modelling of atomically-driven phenomena in bcc tungsten, and the further development of its potentials. read less NOT USED (high confidence) W. Zhou, C. Zhang, Y. G. Li, and Z. Zeng, “Creeping Motion of Self Interstitial Atom Clusters in Tungsten,” Scientific Reports. 2014. link Times cited: 17 NOT USED (high confidence) M. Cak, T. Hammerschmidt, J. Rogal, V. Vítek, and R. Drautz, “Analytic bond-order potentials for the bcc refractory metals Nb, Ta, Mo and W,” Journal of Physics: Condensed Matter. 2014. link Times cited: 20 Abstract: Bond-order potentials (BOPs) are based on the tight-binding … read moreAbstract: Bond-order potentials (BOPs) are based on the tight-binding approximation for determining the energy of a system of interacting atoms. The bond energy and forces are computed analytically within the formalism of the analytic BOPs. Here we present parametrizations of the analytic BOPs for the bcc refractory metals Nb, Ta, Mo and W. The parametrizations are optimized for the equilibrium bcc structure and tested for atomic environments far from equilibrium that had not been included in the fitting procedure. These tests include structural energy differences for competing crystal structures; tetragonal, trigonal, hexagonal and orthorhombic deformation paths; formation energies of point defects as well as phonon dispersion relations. Our tests show good agreement with available experimental and theoretical data. In practice, we obtain the energetic ordering of vacancy, [1 1 1], [1 1 0], and [1 0 0] self-interstitial atom in agreement with density functional theory calculations. read less NOT USED (high confidence) W. Setyawan, G. Nandipati, K. Roche, H. Heinisch, B. Wirth, and R. Kurtz, “Displacement cascades and defects annealing in tungsten, Part I: Defect database from molecular dynamics simulations,” Journal of Nuclear Materials. 2014. link Times cited: 93 NOT USED (high confidence) Y.-S. Lin, M. Mrovec, and V. Vitek, “A new method for development of bond-order potentials for transition bcc metals,” Modelling and Simulation in Materials Science and Engineering. 2014. link Times cited: 22 Abstract: A new development of numerical bond-order potentials (BOPs) … read moreAbstract: A new development of numerical bond-order potentials (BOPs) for the non-magnetic transition metals V, Nb, Ta, Cr, Mo and W is presented. The principles on which the BOPs have been set up are the same as in earlier developments (Aoki et al 2007 Prog. Mater. Sci. 52 154). However, the bond integrals are based on the recently advanced method of parametrization of tight-binding from DFT calculations (Madsen et al 2011 Phys. Rev. B 83 4119, Urban et al 2011 Phys. Rev. B 84 155119) and do not require any screening. At the same time, the functional form of the environmentally dependent repulsion is identified with the functional form of the repulsion arising from the overlap of s and p electrons in argon as proposed in Aoki and Kurokawa (2007 J. Phys.: Condens. Matter 19 136228). This is justified by the same physical origin of the environment dependent repulsion, which in transition metals arises from the overlap of s electrons that are being squeezed into the ion core regions under the influence of the strong covalent d bonds. The testing of the developed BOPs involves investigation of alternative higher energy structures, transformation paths connecting the bcc structure with other structures via continuously distorted configurations, evaluation of the vacancy formation energy and calculation of phonon spectra. In all cases, the BOP calculations are in more than satisfactory agreement with either DFT calculations and/or available experimental data. The calculated γ-surfaces for {1 0 1} planes all suggest that the core of 1/2〈1 1 1〉 screw dislocations is non-degenerate in the transition metals. This is also in full agreement with available calculations that account fully for the quantum-mechanical nature of the d electrons that provide the bulk of the bonding in transition metals. The testing of developed BOPs clearly demonstrates that they are transferable to structures well outside the regime of the ideal bcc lattice and are suitable for investigating the atomic structure and behaviour of extended crystal defects. read less NOT USED (high confidence) L. Bukonte, T. Ahlgren, and K. Heinola, “Modelling of monovacancy diffusion in W over wide temperature range,” Journal of Applied Physics. 2014. link Times cited: 18 Abstract: The diffusion of monovacancies in tungsten is studied comput… read moreAbstract: The diffusion of monovacancies in tungsten is studied computationally over a wide temperature range from 1300 K until the melting point of the material. Our modelling is based on Molecular Dynamics technique and Density Functional Theory. The monovacancy migration barriers are calculated using nudged elastic band method for nearest and next-nearest neighbour monovacancy jumps. The diffusion pre-exponential factor for monovacancy diffusion is found to be two to three orders of magnitude higher than commonly used in computational studies, resulting in attempt frequency of the order 1015 Hz. Multiple nearest neighbour jumps of monovacancy are found to play an important role in the contribution to the total diffusion coefficient, especially at temperatures above 2/3 of Tm, resulting in an upward curvature of the Arrhenius diagram. The probabilities for different nearest neighbour jumps for monovacancy in W are calculated at different temperatures. read less NOT USED (high confidence) D. Mason, X. Yi, X. Yi, M. Kirk, and S. Dudarev, “Elastic trapping of dislocation loops in cascades in ion-irradiated tungsten foils,” Journal of Physics: Condensed Matter. 2014. link Times cited: 120 Abstract: Using in situ transmission electron microscopy (TEM), we hav… read moreAbstract: Using in situ transmission electron microscopy (TEM), we have observed nanometre scale dislocation loops formed when an ultra-high-purity tungsten foil is irradiated with a very low fluence of self-ions. Analysis of the TEM images has revealed the largest loops to be predominantly of prismatic 1/2〈111〉 type and of vacancy character. The formation of such dislocation loops is surprising since isolated loops are expected to be highly mobile, and should escape from the foil. In this work we show that the observed size and number density of loops can be explained by the fact that the loops are not isolated—the loops formed in close proximity in the cascades interact with each other and with vacancy clusters, also formed in cascades, through long-range elastic fields, which prevent the escape of loops from the foil. We find that experimental observations are well reproduced by object Kinetic Monte Carlo simulations of evolution of cascades only if elastic interaction between the loops is taken into account. Our analysis highlights the profound effect of elastic interaction between defects on the microstructural evolution of irradiated materials. read less NOT USED (high confidence) M. Marinica et al., “Interatomic potentials for modelling radiation defects and dislocations in tungsten,” Journal of Physics: Condensed Matter. 2013. link Times cited: 258 Abstract: We have developed empirical interatomic potentials for study… read moreAbstract: We have developed empirical interatomic potentials for studying radiation defects and dislocations in tungsten. The potentials use the embedded atom method formalism and are fitted to a mixed database, containing various experimentally measured properties of tungsten and ab initio formation energies of defects, as well as ab initio interatomic forces computed for random liquid configurations. The availability of data on atomic force fields proves critical for the development of the new potentials. Several point and extended defect configurations were used to test the transferability of the potentials. The trends predicted for the Peierls barrier of the 1 2 ⟨ 111 ⟩ ?> screw dislocation are in qualitative agreement with ab initio calculations, enabling quantitative comparison of the predicted kink-pair formation energies with experimental data. read less NOT USED (high confidence) D. Nguyen-Manh, P. Ma, M. Lavrentiev, and S. Dudarev, “Constrained non-collinear magnetism in disordered Fe and Fe-Cr alloys,” International Conference on Supercomputing. 2013. link Times cited: 8 Abstract: The development of quantitative models for radiation damage … read moreAbstract: The development of quantitative models for radiation damage effects in iron, iron alloys and steels, particularly for the high temperature properties of the alloys, requires understanding of magnetic interactions, which control the phase stability of ferritic-martensitic, ferritic, and austenitic steels. In this work, disordered magnetic configurations of pure iron and Fe-Cr alloys are investigated using Density Functional Theory (DFT) formalism, in the form of constrained non-collinear magnetic calculations, with the objective of creating a database of atomic magnetic moments and forces acting between the atoms. From a given disordered atomic configuration of either pure Fe or Fe-Cr alloy, a penalty contribution to the usual spin-polarized DFT total energy has been calculated by constraining the magnitude and direction of magnetic moments. An extensive database of non-collinear magnetic moment and force components for various atomic configurations has been generated and used for interpolating the spatially-dependent magnetic interaction parameters, for applications in large-scale spin-lattice dynamics and magnetic Monte-Carlo simulations. read less NOT USED (high confidence) G. Bonny, N. Castin, J. Bullens, A. Bakaev, T. Klaver, and D. Terentyev, “On the mobility of vacancy clusters in reduced activation steels: an atomistic study in the Fe–Cr–W model alloy,” Journal of Physics: Condensed Matter. 2013. link Times cited: 29 Abstract: Reduced activation steels are considered as structural mater… read moreAbstract: Reduced activation steels are considered as structural materials for future fusion reactors. Besides iron and the main alloying element chromium, these steels contain other minor alloying elements, typically tungsten, vanadium and tantalum. In this work we study the impact of chromium and tungsten, being major alloying elements of ferritic Fe–Cr–W-based steels, on the stability and mobility of vacancy defects, typically formed under irradiation in collision cascades. For this purpose, we perform ab initio calculations, develop a many-body interatomic potential (EAM formalism) for large-scale calculations, validate the potential and apply it using an atomistic kinetic Monte Carlo method to characterize the lifetime and diffusivity of vacancy clusters. To distinguish the role of Cr and W we perform atomistic kinetic Monte Carlo simulations in Fe–Cr, Fe–W and Fe–Cr–W alloys. Within the limitation of transferability of the potentials it is found that both Cr and W enhance the diffusivity of vacancy clusters, while only W strongly reduces their lifetime. The cluster lifetime reduction increases with W concentration and saturates at about 1–2 at.%. The obtained results imply that W acts as an efficient ‘breaker’ of small migrating vacancy clusters and therefore the short-term annealing process of cascade debris is modified by the presence of W, even in small concentrations. read less NOT USED (high confidence) J. Wang, Y. Zhou, M. Li, and Q. Hou, “A modified W–W interatomic potential based on ab initio calculations,” Modelling and Simulation in Materials Science and Engineering. 2013. link Times cited: 35 Abstract: In this paper we have developed a Finnis–Sinclair-type inter… read moreAbstract: In this paper we have developed a Finnis–Sinclair-type interatomic potential for W–W interactions that is based on ab initio calculations. The modified potential is able to reproduce the correct formation energies of self-interstitial atom (SIA) defects in tungsten, offering a significant improvement over the Ackland–Thetford tungsten potential. Using the modified potential, the thermal expansion is calculated in a temperature range from 0 to 3500 K. The results are in reasonable agreement with the experimental data, thus overcoming the shortcomings of the negative thermal expansion using the Derlet–Nguyen–Manh–Dudarev tungsten potential. The W–W potential presented here is also applied to study in detail the diffusion of SIAs in tungsten. We reveal that the initial SIA initiates a sequence of tungsten atom displacements and replacements in the 〈1 1 1〉 direction. An Arrhenius fit to the diffusion data at temperatures below 550 K indicates a migration energy of 0.022 eV, which is in reasonable agreement with the experimental data. read less NOT USED (high confidence) V. Borovikov, X. Tang, D. Perez, X. Bai, B. Uberuaga, and A. Voter, “Coupled motion of grain boundaries in bcc tungsten as a possible radiation-damage healing mechanism under fusion reactor conditions,” Nuclear Fusion. 2013. link Times cited: 36 Abstract: As a potential first-wall fusion reactor material, tungsten … read moreAbstract: As a potential first-wall fusion reactor material, tungsten will be subjected to high radiation flux and extreme mechanical stress. We propose that under these conditions, coupled grain boundary (GB) motion, in some cases enhanced by interstitial loading, can lead to a radiation-damage healing mechanism, in which a large stress activates coupled GB motion, and the GB sweeps up the defects, such as voids and vacancies, as it passes through the material. The stress-induced mobility characteristics of a number of GBs in tungsten are examined to investigate the likelihood of this scenario. read less NOT USED (high confidence) A. Kuksin and A. Yanilkin, “Atomistic simulation of the motion of dislocations in metals under phonon drag conditions,” Physics of the Solid State. 2013. link Times cited: 51 NOT USED (high confidence) D. Smirnova et al., “A ternary EAM interatomic potential for U–Mo alloys with xenon,” Modelling and Simulation in Materials Science and Engineering. 2013. link Times cited: 71 Abstract: A new interatomic potential for a uranium–molybdenum system … read moreAbstract: A new interatomic potential for a uranium–molybdenum system with xenon is developed in the framework of an embedded atom model using a force-matching technique and a dataset of ab initio atomic forces. The verification of the potential proves that it is suitable for the investigation of various compounds existing in the system as well as for simulation of pure elements: U, Mo and Xe. Computed lattice constants, thermal expansion coefficients, elastic properties and melting temperatures of U, Mo and Xe are consistent with the experimentally measured values. The energies of the point defect formation in pure U and Mo are proved to be comparable to the density-functional theory calculations. We compare this new U–Mo–Xe potential with the previously developed U and Mo–Xe potentials. A comparative study between the different potential functions is provided. The key purpose of the new model is to study the atomistic processes of defect evolution taking place in the U–Mo nuclear fuel. Here we use the potential to simulate bcc alloys containing 10 wt% of intermetallic Mo and U2Mo. read less NOT USED (high confidence) L. Zhang, E. Martínez, A. Caro, X.-Y. Liu, and M. Demkowicz, “Liquid-phase thermodynamics and structures in the Cu–Nb binary system,” Modelling and Simulation in Materials Science and Engineering. 2013. link Times cited: 37 Abstract: An embedded atom method (EAM) interatomic potential is const… read moreAbstract: An embedded atom method (EAM) interatomic potential is constructed to reproduce the main topological features of the experimental equilibrium phase diagram of the Cu–Nb system in both solid and liquid states. The potential is fitted to composition-dependent enthalpies of mixing for bcc and fcc random solid solutions obtained from first-principles calculations at 0 K. Compared with two other EAM Cu–Nb potentials in the literature, the phase diagram of the current potential shows better agreement with the experimental phase diagram. Our potential predicts that the Cu–Nb liquid phase at equilibrium is compositionally patterned over lengths of about 2.3 nm. The newly constructed potential may be used to study the effect of liquid thermodynamics and structure on properties of binary systems, such as radiation-induced mixing. read less NOT USED (high confidence) L. Proville, D. Rodney, and M. Marinica, “Quantum effect on thermally activated glide of dislocations.,” Nature materials. 2012. link Times cited: 192 NOT USED (high confidence) Y. Li, W. Zhou, L. Huang, R. Ning, Z. Zhi, and J. Xin, “The Accumulation of He on a W Surface During keV-He Irradiation: Cluster Dynamics Modeling ⁄,” Plasma Science & Technology. 2012. link Times cited: 7 Abstract: The accumulation of He on a W surface during keV-He ion irra… read moreAbstract: The accumulation of He on a W surface during keV-He ion irradiation has been simulated using cluster dynamics modeling. This is based mainly on rate theory and improved by involving difierent types of objects, adopting up-to-date parameters and complex reaction processes, as well as considering the difiusion process along with depth. These new features make the simulated results compare very well with the experimental ones. The accumulation and difiusion processes are analyzed, and the depth and size dependence of the He concentrations contributed by difierent types of He clusters is also discussed. The exploration of the trapping and difiusion efiects of the He atoms is helpful in understanding the evolution of the damages in the near-surface of plasma-facing materials under He ion irradiation. read less NOT USED (high confidence) D. Nguyen-Manh, M. Lavrentiev, M. Muzyk, and S. Dudarev, “First-principles models for phase stability and radiation defects in structural materials for future fusion power-plant applications,” Journal of Materials Science. 2012. link Times cited: 25 NOT USED (high confidence) Z. Insepov et al., “Derivation of kinetic coefficients by atomistic methods for studying defect behavior in Mo,” Journal of Nuclear Materials. 2012. link Times cited: 15 NOT USED (high confidence) L. Ventelon, F. Willaime, C. Fu, M. Héran, and I. Ginoux, “Ab initio investigation of radiation defects in tungsten: Structure of self-interstitials and specificity of di-vacancies compared to other bcc transition metals,” Journal of Nuclear Materials. 2012. link Times cited: 94 NOT USED (high confidence) L. Chen, Y. Liu, H.-mei Zhou, S. Jin, Y. Zhang, and G. Lu, “Stability and diffusion properties of self-interstitial atoms in tungsten: a first-principles investigation,” Science China Physics, Mechanics and Astronomy. 2012. link Times cited: 0 NOT USED (high confidence) L. Chen, Y.-L. Liu, H.-B. Zhou, S. Jin, Y. Zhang, and G. Lu, “Stability and diffusion properties of self-interstitial atoms in tungsten: a first-principles investigation,” Science China Physics, Mechanics and Astronomy. 2012. link Times cited: 21 NOT USED (high confidence) C. Becquart, M. Barthe, and A. D. Backer, “Modelling radiation damage and He production in tungsten,” Physica Scripta. 2011. link Times cited: 31 Abstract: Tungsten is a candidate material for the divertor and for fi… read moreAbstract: Tungsten is a candidate material for the divertor and for first wall armor of future thermonuclear fusion reactors (ITER and DEMO). In such irradiation conditions, it is well known that the microstructure, and as a result the properties of the materials, will evolve. In this perspective, the fate of irradiation-induced defects (helium atoms, vacancies, self-interstitials and the complexes they can form) has to be understood. In particular, He migration properties are of fundamental as well as practical interest, as they can affect the microstructure evolution and eventually influence physical and mechanical properties, the most significant example being high-temperature helium embrittlement. In this work, we show how our ab initio parameterized object kinetic Monte Carlo code LAKIMOCA can model the evolution, during implantation, of the point defect population in the track region of 800 keV 3He atoms implanted in W samples. We also discuss possible improvements of the model. read less NOT USED (high confidence) D. Duffy, “Modelling materials for fusion power,” International Materials Reviews. 2011. link Times cited: 12 Abstract: Fusion has the potential for delivering safe, clean, low car… read moreAbstract: Fusion has the potential for delivering safe, clean, low carbon power; however, significant scientific and engineering hurdles must first be overcome. One such hurdle is the design of materials that will withstand the harsh conditions. The materials which line the vessel walls will experience exceptionally high heat and particle fluxes, which will gradually erode the materials and contaminate the plasma. The deuterium–tritium fusion reaction will produce high energy neutrons, which will create defects and transmutation reactions in the vessel walls. These defects, along with the transmutation gasses, evolve over time and change the microstructure and properties of the material. In order to design suitable materials for fusion, the radiation damage, and its evolution over time, must be understood and evaluated for a broad class of materials. Modelling has a vital role to play because it can provide details about processes that occur on length and timescales that are inaccessible to experiment. In this review, the challenges that face designers of fusion power plants are discussed. The modelling techniques that are used to model radiation effects are described and the links between modelling and experiment are discussed. The review concludes with a discussion about the future direction for fusion materials research. read less NOT USED (high confidence) N. Baluc et al., “From materials development to their test in IFMIF: an overview,” Nuclear Fusion. 2011. link Times cited: 6 Abstract: R&D activities on fusion reactor materials in Switzerland fo… read moreAbstract: R&D activities on fusion reactor materials in Switzerland focus on (1) the development of advanced metallic materials for structural applications in plasma-facing (first wall, divertor) and breeding blanket components of the future fusion power reactors, in particular oxide dispersion strengthened reduced activation ferritic steels and tungsten-base materials, (2) the modelling of radiation damage and radiation effects and (3) small specimen test technology for the future International Fusion Materials Irradiation Facility. The main objectives, examples of recent results and future activities are described in the case of these three R&D areas. read less NOT USED (high confidence) S. Chiesa, P. Derlet, S. Dudarev, and H. Swygenhoven, “Optimization of the magnetic potential for α-Fe,” Journal of Physics: Condensed Matter. 2011. link Times cited: 46 Abstract: A second generation of empirical potentials is produced for … read moreAbstract: A second generation of empirical potentials is produced for α-Fe within the framework of the magnetic potential formalism (Dudarev and Derlet 2005 J. Phys.: Condens. Matter 17 7097). A materials database that, in addition to ab initio-derived point defect formation energies, now includes third-order elastic constant and ab initio-derived string potential data controlling, respectively, the thermal expansion properties and the core structure of the 1/2⟨111⟩ screw dislocation. Three parameterizations are presented in detail, all of which exhibit positive thermal expansion and produce a non-degenerate configuration for the relaxed 1/2⟨111⟩ screw dislocation easy core structure. These potentials, along with two other published potentials, are investigated in terms of defect formation volume, early stage dislocation loop clustering energetics, ⟨110⟩ dumbbell interstitial diffusion, and the zero-stress 1/2⟨111⟩ screw dislocation Peierls barrier and its corresponding kink formation energies. read less NOT USED (high confidence) A. Kashinath and M. Demkowicz, “A predictive interatomic potential for He in Cu and Nb,” Modelling and Simulation in Materials Science and Engineering. 2011. link Times cited: 53 Abstract: First principles calculations show that two-body forces are … read moreAbstract: First principles calculations show that two-body forces are sufficient to describe interactions of He with fcc Cu and bcc Nb. This property is explained directly from calculated charge density distributions and used to construct a Cu–Nb–He interatomic potential that predicts accurate He impurity energies despite not being fitted to them. read less NOT USED (high confidence) T. Amino, K. Arakawa, and H. Mori, “Activation energy for long-range migration of self-interstitial atoms in tungsten obtained by direct measurement of radiation-induced point-defect clusters,” Philosophical Magazine Letters. 2011. link Times cited: 25 Abstract: The activation energy for the long-range intrinsic migration… read moreAbstract: The activation energy for the long-range intrinsic migration of self-interstitial atoms (SIAs) in metals, , is an important physical quantity closely associated with microstructural evolution upon energetic particle irradiation. The values for various metals have been widely investigated through recovery experiments on specimens irradiated at low temperatures upon thermal annealing, and the values have been estimated from the dependence of measured quantities of the specimens on the annealing temperature. On the other hand, the dependence of measured quantities on irradiation temperature is also expected to reflect the values. It is of importance to compare the values obtained by these two different kinds of experiments. However, no systematic studies have been carried out along the latter line. In this study, the number densities of SIA clusters formed in tungsten upon high-energy electron irradiation are directly measured as a function of the irradiation temperature using high-voltage electron microscopy. The analysis of the experimental data shows that the value is in the range from 0.088 to 0.102 eV or it is less than 0.046 eV. These values are consistent with those obtained in a recovery experiment and a theoretical study, respectively. read less NOT USED (high confidence) B. Y. D. M. Duffy and D. Duffy, “Fusion power: a challenge for materials science,” Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 2010. link Times cited: 66 Abstract: The selection and design of materials that will withstand th… read moreAbstract: The selection and design of materials that will withstand the extreme conditions of a fusion power plant has been described as one of the greatest materials science challenges in history. The high particle flux, high thermal load, thermal mechanical stress and the production of transmutation elements combine to produce a uniquely hostile environment. In this paper, the materials favoured for the diverse roles in a fusion power plant are discussed, along with the experimental and modelling techniques that are used to advance the understanding of radiation damage in materials. Areas where further research is necessary are highlighted. read less NOT USED (high confidence) N. Juslin, V. Jansson, and K. Nordlund, “Simulation of cascades in tungsten–helium,” Philosophical Magazine. 2010. link Times cited: 34 Abstract: Helium (He) is present in fusion reactor wall materials, and… read moreAbstract: Helium (He) is present in fusion reactor wall materials, and its effect on radiation damage must be taken into account. The effect of He on displacement cascades in tungsten (W) has been studied using molecular dynamics simulations. Three different W–W potentials were compared and found to differ, especially for the clustering of the vacancies formed in the cascades. While there are differences in the amounts of damage depending on the potential, the overall effect of He in interstitial positions was to increase the amount of damage, while He in substitutional positions reduces it, due to the effect He has on the recombination of tungsten interstititals. read less NOT USED (high confidence) T. Ahlgren, K. Heinola, N. Juslin, and A. Kuronen, “Bond-order potential for point and extended defect simulations in tungsten,” Journal of Applied Physics. 2010. link Times cited: 80 Abstract: A reactive interatomic bond-order potential for bcc tungsten… read moreAbstract: A reactive interatomic bond-order potential for bcc tungsten is presented. Special attention in the potential development was given for obtaining accurate formation and migration energies for point defects, making the potential useful in atomic scale simulations of point and extended defects. The potential was used to calculate binding energies and trapping distances for vacancies in vacancy clusters and the recombination radius for self-interstitial atom and monovacancy. read less NOT USED (high confidence) S. Chiesa, M. R. Gilbert, S. Dudarev, P. Derlet, and H. Swygenhoven, “The non-degenerate core structure of a ½⟨111⟩ screw dislocation in bcc transition metals modelled using Finnis–Sinclair potentials: The necessary and sufficient conditions,” Philosophical Magazine. 2009. link Times cited: 30 Abstract: It is shown that semi-empirical potentials for bcc metals ba… read moreAbstract: It is shown that semi-empirical potentials for bcc metals based on the non-directional second-moment Finnis–Sinclair approximation are able to predict, as a matter of routine, the non-degenerate core structure for the perfect ½⟨111⟩ dislocation if they correctly describe the inter-string pair potential of a rigid multi-string Frenkel–Kontorova model for the corresponding ideal bcc lattice. We prove this by inspecting the previously published empirical potentials, and also by performing an extensive search in functional parameter space for an optimal parameterisation of the magnetic potential formalism for bcc ferromagnetic Fe. read less NOT USED (high confidence) T. Parolin et al., “Nuclear magnetic resonance study of Li implanted in a thin film of niobium,” Physical Review B. 2009. link Times cited: 16 Abstract: We report results of beta-detected NMR of ${^{8}\text{L}\tex… read moreAbstract: We report results of beta-detected NMR of ${^{8}\text{L}\text{i}}^{+}$ implanted in Nb at high magnetic field. We identify two distinct sites for $^{8}\text{L}\text{i}$ in the body-centered lattice. At low temperature, the site is characterized by a well-defined quadrupolar splitting. At about 50 K this site becomes unstable. Close to room temperature, Li occupies the cubic substitutional site. Spin-lattice relaxation measurements are consistent with a site-dependent coupling to the Nb conduction electrons and suggest that the site change proceeds in two steps. We report Knight shifts for the two well-defined sites and perform a Korringa analysis. read less NOT USED (high confidence) M. Demkowicz and R. Hoagland, “Simulations of Collision Cascades in Cu–Nb Layered Composites Using an EAM Interatomic Potential.” 2009. link Times cited: 77 Abstract: The embedded atom method (EAM) is used to construct an inter… read moreAbstract: The embedded atom method (EAM) is used to construct an interatomic potential for modelling interfaces in Cu–Nb nanocomposites. Implementation of the Ziegler–Biersack–Littmark (ZBL) model for short-range interatomic interactions enables studies of response to ion bombardment. Collision cascades are modelled in fcc Cu, bcc Nb, and in Cu–Nb layered composites in the experimentally-observed Kurdjumov–Sachs (KS) orientation relation. The interfaces in these composites reduce the number of vacancies and interstitials created per keV of the primary knock-on atom (PKA) by 50–70% compared to fcc Cu or bcc Nb. read less NOT USED (high confidence) S. Chiesa, P. Derlet, and S. Dudarev, “Free energy of a ⟨110⟩ dumbbell interstitial defect in bcc Fe: Harmonic and anharmonic contributions,” Physical Review B. 2009. link Times cited: 35 Abstract: S. Chiesa,1 P. M. Derlet,2 and S. L. Dudarev3,4 1NUM/ASQ-Mat… read moreAbstract: S. Chiesa,1 P. M. Derlet,2 and S. L. Dudarev3,4 1NUM/ASQ-Materials Science and Simulation, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland 2NUM-Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland 3Culham Science Centre, EURATOM/UKAEA Fusion Association, Oxfordshire OX14 3DB, United Kingdom 4Department of Physics, Imperial College, Exhibition Road, London SW7 2AZ, United Kingdom Received 7 April 2009; revised manuscript received 22 May 2009; published 17 June 2009 read less NOT USED (high confidence) S. Dudarev et al., “The EU programme for modelling radiation effects in fusion reactor materials: An overview of recent advances and future goals,” Journal of Nuclear Materials. 2009. link Times cited: 80 NOT USED (high confidence) S. Khakshouri, D. Alfé, and D. Duffy, “Development of an electron-temperature-dependent interatomic potential for molecular dynamics simulation of tungsten under electronic excitation,” Physical Review B. 2008. link Times cited: 61 Abstract: Irradiation of a metal by lasers or swift heavy ions causes … read moreAbstract: Irradiation of a metal by lasers or swift heavy ions causes the electrons to become excited. In the vicinity of the excitation, an electronic temperature is established within a thermalization time of 10-100 fs, as a result of electron-electron collisions. For short times, corresponding to less than 1 ps after excitation, the resulting electronic temperature may be orders of magnitude higher than the lattice temperature. During this short time, atoms in the metal experience modified interatomic forces as a result of the excited electrons. These forces can lead to ultrafast nonthermal phenomena such as melting, ablation, laser-induced phase transitions, and modified vibrational properties. We develop an electron-temperature-dependent empirical interatomic potential for tungsten that can be used to model such phenomena using classical molecular dynamics simulations. Finite-temperature density functional theory calculations at high electronic temperatures are used to parametrize the model potential. read less NOT USED (high confidence) A. Semenov, C. Woo, and W. Frank, “Diffusion anisotropy and void development under cascade irradiation,” Applied Physics A. 2008. link Times cited: 16 NOT USED (high confidence) D. Nguyen-Manh, M. Mrovec, and S. Fitzgerald, “Dislocation Driven Problems in Atomistic Modelling of Materials,” Materials Transactions. 2008. link Times cited: 21 Abstract: Understanding the mechanical properties of technologically a… read moreAbstract: Understanding the mechanical properties of technologically advanced materials from quantum mechanical predictions based on electronic structure calculations remains one of the most challenging problems in modern computational materials science. In this paper, we illustrate this challenge from our current investigations on dislocation behaviour in bcc transition metals that are promising candidates for materials subject to fast neutron irradiations in future fusion power plants. Starting with the relationship between the brittleness and the negative Cauchy pressure of elastic constants in materials within the so-called Harris-Foulkes approximation to the density functional theory (DFT), we briefly discuss the importance of the generic form of interatomic potentials in order to reproduce a correct Cauchy pressure. The latter in turn plays an important role in predicting dislocation properties in fcc iridium and therefore allows us to explain experimental observation of the intrinsic brittleness of this material. We then investigate the behaviour of the (1/2)[111] screw dislocation that controls plastic deformation in bcc metals from atomistic simulation. Here we show the atomic phenomena associated with the non-planar core structure of dislocations in bcc iron from the Stoner tight-binding bond model. The crucial point comes from the accurate evaluation of forces implemented within the charge neutrality conditions in the treatment of the spin-polarized dependence in the electronic structure calculations. In agreement with DFT studies, the magnetic bond-order potentials predict a non-degenerate core structure for screw dislocations in Fe. Finally, a new analytic expression has been derived for the migration energy barrier for the one-dimensional (1D) motion of crowdions, which are the most stable self-interstitial atom (SIA) defects predicted by our DFT calculations. Importantly, the latter study is strongly supported by the recent observation of 1D diffusion of nanometer-sized dislocation loops, observed very recently under in situ electron microscope irradiation for bcc transition metals. read less NOT USED (high confidence) S. Dudarev, “The non-Arrhenius migration of interstitial defects in bcc transition metals.” 2008. link Times cited: 54 NOT USED (high confidence) Z.-Z. Li et al., “Understanding the Formation Mechanism of Void Lattice Under Irradiation: From Collision Cascades to Self-Assembled Nanovoids,” Computational Materials Science eJournal. 2021. link Times cited: 0 Abstract: The formation of periodic arrangements of voids is an intere… read moreAbstract: The formation of periodic arrangements of voids is an interesting phenomenon occurring in materials under neutron irradiation, usually replicating the symmetry and crystallographic orientation of the host matrix, hence called “void lattice”. Here, taking tungsten as an example, we explore the formation mechanism of the void lattice using an object kinetic Monte Carlo (OKMC) model through the collision cascades simulated using molecular dynamics method. Specifically, the detailed processes from the chaotic neutron irradiation defects to the observable void lattice are obtained via OKMC simulation, which is a prerequisite for understanding its formation mechanism. The formation of the void lattice could be divided into three stages: nucleation, incubation and growth. Both the one-dimensional (1D) migration of SIAs and the fraction of clustered vacancies in cascades play a critical role in the emergence of the void lattice. On the one hand, the 1D migration of SIAs leads to the mutual protection of voids aligned in <111> directions. The self-shielded voids may therefore grow faster compared to the unaligned ones. On the other hand, a moderate fraction of clustered vacancies in cascades guarantees a stable rate for both nucleation and growth of voids. Once the density of the <111> aligned voids reaches a critical value, the dissolution rate of the unaligned voids will overwhelm their nucleation rate, leading to the formation of void-free channels and thus the void lattice. Our results reveal the interrelated mechanism of the 1D migration of SIAs and intra-cascade vacancy clustering for the formation of the void lattice under neutron irradiation, which improves our fundamental understanding of the self-assembled microstructures in irradiated materials. read less NOT USED (high confidence) C. English, “Radiation Damage in Materials.” 2020. link Times cited: 1 Abstract: OBJECTIVES: After completing this module you will be able to… read moreAbstract: OBJECTIVES: After completing this module you will be able to: Explain why ionizing radiation has little effect on metals and their mechanical properties. but creates significant damage in non-metals. 4.2 a) Describe the damage created in metals by fast neutrons. b) Explain how this damage affects: strength, hardness and ductility. 4.3 Explain why elevated operating temperatures reduce the effects of fast neutron damage. 4.4 State the affect of thennal neutrons on the properties of metals. 4.5 Describe the effect of radiation on: (a) oBs and greases, (b) plastics and rubbers, 4.6 a) Explain how radiation affects the structural integrity and shielding properties of concrete, b) State how damage to concrete biological shielding is avoided. read less NOT USED (high confidence) G. V. Alberdi, “Object kinetic Monte Carlo simulations of irradiated tungsten for nuclear fusion reactors.” 2016. link Times cited: 1 |
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