Finnis-Sinclair potential (LAMMPS cubic hermite tabulation) for W developed by Marinica et al. (2013); Potential EAM4 v000

François Willaime; Laurent Proville; Guy Bencteux; Mihai-Cosmin Marinica; Lisa Ventelon; Mark R. Gilbert; Sergei Dudarev; Jaime Marian

doi:10.25950/ce93b9c6

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EAM_Dynamo_MarinicaVentelonGilbert_2013EAM4__MO_046576227003_000

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Interatomic potential for Tungsten (W).
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Title A single sentence description.	Finnis-Sinclair potential (LAMMPS cubic hermite tabulation) for W developed by Marinica et al. (2013); Potential EAM4 v000
Description A short description of the Model describing its key features including for example: type of model (pair potential, 3-body potential, EAM, etc.), modeled species (Ac, Ag, ..., Zr), intended purpose, origin, and so on.	Finnis-Sinclair potential for W developed by Marinica et al. (2013); Potential EAM4. 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.
Species The supported atomic species.	W
Disclaimer A statement of applicability provided by the contributor, informing users of the intended use of this KIM Item.	None
Content Origin	NIST IPRP (https://www.ctcms.nist.gov/potentials/W.html)

Contributor	Ellad B. Tadmor
Maintainer	Ellad B. Tadmor
Developer	François Willaime Laurent Proville Guy Bencteux Mihai-Cosmin Marinica Lisa Ventelon Mark R. Gilbert Sergei Dudarev Jaime Marian
Published on KIM	2018
How to Cite	Click here to download this citation in BibTeX format.
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See the Deep Citation documentation for more information. 239 Citations (184 used) Show Model Used Show All Help us to determine which of the papers that cite this potential actually used it to perform calculations. If you know, click the . J. Liu, J. Byggmästar, Z. Fan, P. Qian, and Y. Su, “Large-scale machine-learning molecular dynamics simulation of primary radiation damage in tungsten,” Physical Review B. 2023. link Times cited: 4 Abstract: Simulating collision cascades and radiation damage poses a l… read more Abstract: Simulating collision cascades and radiation damage poses a long-standing challenge for existing interatomic potentials, both in terms of accuracy and efficiency. Machine-learning based interatomic potentials have shown sufficiently high accuracy for radiation damage simulations, but most existing ones are still not efficient enough to model high-energy collision cascades with sufficiently large space and time scales. To this end, we here extend the highly efficient neuroevolution potential (NEP) framework by combining it with the Ziegler-Biersack-Littmark (ZBL) screened nuclear repulsion potential, obtaining a NEP-ZBL framework. We train a NEP-ZBL model for tungsten and demonstrate its accuracy in terms of the elastic properties, melting point, and various energetics of defects that are relevant for radiation damage. We then perform large-scale molecular dynamics simulations with the NEP-ZBL model with up to 8.1 million atoms and 240 ps (using a single 40-GB A100 GPU) to study the difference of primary radiation damage in both bulk and thin-foil tungsten. While our findings for bulk tungsten are consistent with existing results simulated by embedded atom method (EAM) models, the radiation damage differs significantly in foils and shows that larger and more vacancy clusters as well as smaller and fewer interstitial clusters are produced due to the presence of a free surface. read less P. Grigorev, A. Goryaeva, M. Marinica, J. Kermode, and T. Swinburne, “Calculation of dislocation binding to helium-vacancy defects in tungsten using hybrid ab initio-machine learning methods,” Acta Materialia. 2023. link Times cited: 6 L. Reali, M. Gilbert, M. Boleininger, and S. Dudarev, “Intense γ -Photon and High-Energy Electron Production by Neutron Irradiation: Effects of Nuclear Excitations on Reactor Materials,” PRX Energy. 2022. link Times cited: 1 Abstract: The effects of neutron irradiation on materials are often in… read more Abstract: The effects of neutron irradiation on materials are often interpreted in terms of atomic recoils, initiated by neutron impacts and producing crystal lattice defects. In addition, there is a remarkable two-step process, strongly pronounced in the medium-weight and heavy elements. This process involves the generation of energetic {\gamma} photons in nonelastic collisions of neutrons with atomic nuclei, achieved via capture and inelastic reactions. Subsequently, high-energy electrons are excited through the scattering of {\gamma} photons by the atomic electrons. We derive and validate equations enabling a fast and robust evaluation of photon and electron fluxes produced by the neutrons in the bulk of materials. The two-step n-{\gamma}-e scattering creates a nonequilibrium dynamically fluctuating steady-state population of high-energy electrons, with the spectra of photon and electron energies extending well into the mega-electron-volt range. This stimulates vacancy diffusion through electron-triggered atomic recoils, primarily involving vacancy-impurity dissociation, even if thermal activation is ineffective. Tungsten converts the energy of fusion or fission neutrons into a flux of {\gamma} radiation at the conversion efficiency approaching 99%, with implications for structural materials, superconductors, and insulators, as well as phenomena like corrosion, and helium and hydrogen isotope retention. read less J. Qi, C. Oberdorfer, E. Marquis, and W. Windl, “Origin of Enhanced Zone Lines in Field Desorption Maps,” SSRN Electronic Journal. 2022. link Times cited: 1 Abstract: Artifacts in the collective desorption map of the detector h… read more Abstract: Artifacts in the collective desorption map of the detector hits impede a truthful reconstruction, including enhanced"zone lines"with high atomic impact intensity. Since APT is destructive, simulation is the only approach to explain the origin of these zone lines, but previous work couldn't reproduce them. Here, we use a new simulation technique that adds the full electrostatic forces to the interatomic forces in a molecular-dynamics simulation and eliminates the previous ad-hoc assumptions. We find for the canonical example of tungsten that evaporation happens when the electrostatic force overpowers the interatomic force, and the misalignment of the two forces deviates the launch direction of the atoms in certain zones, giving rise to an accumulation of hit events around zone lines. read less J. Cui et al., “Effect of twin boundaries on the strength of body-centered cubic tungsten nanowires,” Materials Science and Engineering: A. 2022. link Times cited: 2 B. Sun, D. Maroudas, B. Wirth, and E. Martínez, “Strain Effects on the Diffusion Properties of Near-Surface Self-Interstitial Atoms and Adatoms in Tungsten,” Frontiers in Materials. 2021. link Times cited: 2 Abstract: Tungsten (W) is a candidate for the plasma-facing components… read more Abstract: Tungsten (W) is a candidate for the plasma-facing components and divertor in future fusion applications. The material will be subject to a large particle influx (mainly helium and hydrogenic species) that will form bubbles. As bubbles grow, they compress the material, adding to thermal stresses, and eject self-interstitial atoms (SIAs—isolated or in clusters) to release internal pressure. These SIAs diffuse towards the surface in large stress/strain fields and on the surface are thought to act as precursors for nanotendril formation (also known as fuzz) that develops on the material surface modifying its morphology. In this work we analyze the effect of strain on the diffusion properties of both SIAs and adatoms. Relying on atomistic simulations, we compute the average time that a SIA created in the center of a tungsten slab takes to reach a (110) surface for different strains and temperatures. This time relates to the SIA diffusivity and allows to compute the activation energy and dipole tensor including surface effects. We observe a large strain effect that significantly modifies the propensity for SIAs to reach the surface and, hence, to cluster to form dislocation loops in the bulk crystal. Strain also alters the diffusivity of the adatom although to a lesser extent. Finally, we report on the resulting surface roughness evolution and its dependence on strain. read less S. Kawano and J. Mason, “Classification of atomic environments via the Gromov–Wasserstein distance,” Computational Materials Science. 2020. link Times cited: 5 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 more Abstract: 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 K. V. Reddy and S. Pal, “Atomistic Simulation of Nano-Rolling Process for Nanocrystalline Tungsten,” JOM. 2020. link Times cited: 5 M. Boleininger, T. Swinburne, L. Dupuy, and S. Dudarev, “Ultraviolet catastrophe of a fluctuating curved dislocation line.” 2020. link Times cited: 5 Abstract: The authors demonstrate that the line tension expression for… read more Abstract: The authors demonstrate that the line tension expression for dislocation core energy and the regularization of elastic fields near the core fundamentally emerge from the periodicity of the discrete atomic lattice. A continuum model for the dislocation core is presented which addresses the problem of short wavelength instability of dislocation lines inherent to linear elasticity theory, and predicts configurational energies. read less P. Díaz-Rodríguez et al., “Highly porous tungsten for plasma-facing applications in nuclear fusion power plants: a computational analysis of hollow nanoparticles,” Nuclear Fusion. 2020. link Times cited: 3 Abstract: Plasma-facing materials (PFMs) for nuclear fusion, either in… read more Abstract: Plasma-facing materials (PFMs) for nuclear fusion, either in inertial confinement fusion (ICF) or in magnetic confinement fusion (MCF) approaches, must withstand extremely hostile irradiation conditions. Mitigation strategies are plausible in some cases, but usually the best, or even the only, solution for feasible plant designs is to rely on PFMs able to tolerate these irradiation conditions. Unfortunately, many studies report a lack of appropriate materials that have a good thermomechanical response and are not prone to deterioration by means of irradiation damage. The most deleterious effects are vacancy clustering and the retention of light species, as is the case for tungsten. In an attempt to find new radiation-resistant materials, we studied tungsten hollow nanoparticles under different irradiation scenarios that mimic ICF and MCF conditions. By means of classical molecular dynamics, we determined that these particles can resist astonishingly high temperatures (up to ∼3000 K) and huge internal pressures (>5 GPa at 3000 K) before rupture. In addition, in the case of gentle pressure increase (ICF scenarios), a self-healing mechanism leads to the formation of an opening through which gas atoms are able to escape. The opening disappears as the pressure drops, restoring the original particle. Regarding radiation damage, object kinetic Monte Carlo simulations show an additional self-healing mechanism. At the temperatures of interest, defects (including clusters) easily reach the nanoparticle surface and disappear, which makes the hollow nanoparticles promising for ICF designs. The situation is less promising for MCF because the huge ion densities expected at the surface of PFMs lead to inevitable particle rupture. read less T. Swinburne and D. Perez, “Automated calculation and convergence of defect transport tensors,” npj Computational Materials. 2020. link Times cited: 7 P. Derlet and S. Dudarev, “Microscopic structure of a heavily irradiated material,” Physical Review Materials. 2020. link Times cited: 48 Abstract: New generation nuclear fission and future fusion reactors pr… read more Abstract: New generation nuclear fission and future fusion reactors provide one approach to address the world's increasing energy requirements. The irradiation of fission/fusion components can lead to fundamental changes in material properties that affect the stability and performance of not only the material component but that of the entire reactor. How does the material state evolve with respect to the irradiation dose, and can there exist a microstructure resistant to further irradiation? The present work develops a new computationally efficient approach to answer these questions. read less G. Bonny, A. Bakaev, and D. Terentyev, “Assessment of hardening due to non-coherent precipitates in tungsten-rhenium alloys at the atomic scale,” Scientific Reports. 2019. link Times cited: 7 J. Grossi, J. Kohanoff, T. Todorov, E. Artacho, and E. Bringa, “Electronic heat transport versus atomic heating in irradiated short metallic nanowires,” Physical Review B. 2019. link Times cited: 6 Abstract: © 2019 American Physical Society. The twoerature model (TTM)… read more Abstract: © 2019 American Physical Society. The twoerature model (TTM) is commonly used to represent the energy exchange between atoms and electrons in materials under irradiation. In this work we use the TTM coupled to molecular dynamics (TTM-MD) to study swift heavy ion irradiation of Au and W finite nanowires. While no permanent structural modifications are observed in bulk, nanowires behave in a different way depending on thermal conductivity and the electron-phonon coupling parameter. Au is a good heat conductor and it does not transfer energy from electrons to phonons too efficiently. Therefore, energy is quickly carried away from the track so that both electronic and lattice temperatures remain quite uniform across the sample at all times. W has a lower thermal conductivity and a larger electron-phonon coupling, thus supporting an inhomogeneous lattice temperature profile with temperatures well above melting lasting several picoseconds in the irradiated region. Both W and Au nanowires display radiation-induced surface roughening. However, in the case of W there is also sputtering and the formation of a hole in the central part of the wire, purely due to the energy transferred to the atoms by the electrons. The physical mechanisms underlying these findings are rationalized in terms of a combination of sputtering, vacancy formation, and melt flow phenomena. The role of the electron-phonon coupling parameter g is analyzed. read less 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 more Abstract: 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 M. Boleininger and S. Dudarev, “Continuum model for the core of a straight mixed dislocation,” Physical Review Materials. 2019. link Times cited: 8 J. Fang, Y. Chen, N. Gao, W. Hu, F. Gao, and H. Deng, “Clustering and dislocation loop punching induced by different noble gas bubbles in tungsten: a molecular dynamics study,” Modelling and Simulation in Materials Science and Engineering. 2019. link Times cited: 4 Abstract: Different behaviours of noble gas X (X = He or Ne) atoms in … read more Abstract: Different behaviours of noble gas X (X = He or Ne) atoms in the bulk and on the surface of tungsten (W) have been studied with molecular dynamics simulations to explore the fuzz formation induced by different noble gas bubbles. The formation of X clusters and bubbles in bulk W were simulated at temperatures from 400 to 2000 K. The results showed that higher temperature promotes the nucleation of X bubbles, and the sizes of self-interstitial atoms and X-vacancy clusters of Ne in W were larger than those of He in W at nano-scale, which indicates that Ne atoms can be trapped more easily than He atoms in W. The continuous nucleation processes of He/Ne bubbles near the surface of bulk W were also simulated. When the sizes of the X bubbles were large enough, the behaviour of dislocation loop punching was observed for both He and Ne clusters. From the comparison of the pressure of He/Ne bubble, it is found that the He-bubble can induce the loop-punching with lower critical pressure than the case of Ne-bubble. These results indicate a new understanding of noble gas effects in W in fusion reactors. read less A. Bakaev et al., “Interaction of carbon with microstructural defects in a W-Re matrix: An ab initio assessment,” Journal of Applied Physics. 2019. link Times cited: 20 Abstract: The interaction of carbon atoms with point defects and the c… read more Abstract: The interaction of carbon atoms with point defects and the core of edge and screw dislocations with Burgers vector a 0 / 2 ⟨ 111 ⟩ in W and a W-Re matrix is studied by means of ab initio calculations. The structure and energetics of the ground-state atomic configurations are presented and rationalized. It is found that di-vacancies, which are thermally unstable in pure W according to the state-of-the-art ab initio calculations, can nucleate at C and Re-C complexes, which fill the gap in the explanation of the emergence of nanovoids observed experimentally under irradiation. Also, on the basis of the recent experimental evidence and our calculations, the temperature ranges for the manifestation of the yield drop phenomenon, which is related to the obstruction of dislocation motion due to their decoration by impurities such as carbon, are revealed.The interaction of carbon atoms with point defects and the core of edge and screw dislocations with Burgers vector a 0 / 2 ⟨ 111 ⟩ in W and a W-Re matrix is studied by means of ab initio calculations. The structure and energetics of the ground-state atomic configurations are presented and rationalized. It is found that di-vacancies, which are thermally unstable in pure W according to the state-of-the-art ab initio calculations, can nucleate at C and Re-C complexes, which fill the gap in the explanation of the emergence of nanovoids observed experimentally under irradiation. Also, on the basis of the recent experimental evidence and our calculations, the temperature ranges for the manifestation of the yield drop phenomenon, which is related to the obstruction of dislocation motion due to their decoration by impurities such as carbon, are revealed. read less S. Li, S. Cui, H.-W. Chen, J. Li, H. Huang, and H. Luo, “Effect of cooling rates on solidification, microstructure and mechanical properties in tungsten,” CrystEngComm. 2019. link Times cited: 5 Abstract: Tungsten with its excellent high-temperature properties woul… read more Abstract: Tungsten with its excellent high-temperature properties would be a most promising candidate as a plasma-facing material at the divertor in a nuclear fusion plant. read less B. Gurrutxaga-Lerma and J. Verschueren, “Elastic models of dislocations based on atomistic Kanzaki forces,” Physical Review B. 2018. link Times cited: 7 Abstract: © 2018 authors. Published by the American Physical Society. … read more Abstract: © 2018 authors. Published by the American Physical Society. This paper studies the relationship between the atomistic representation of crystalline dislocations as Kanzaki forces and the continuum representation of dislocations as Burridge-Knopoff (BK) force distributions. We first derive a complete theory of the BK force representation of dislocations in an anisotropic linear elastic continuum, showcasing a number of fundamental features found when dislocations are represented as distributions of body forces in defect-free continuum media. We then build, within the harmonic approximation, the Kanzaki force representation of dislocations in atomistic lattice models. We rigorously show that in the long-wave limit, the Kanzaki force representation converges to the continuum BK representation. We therefore justify employing the Kanzaki forces as source terms in continuum theories of dislocations. We do this by establishing a methodology to compute the Kanzaki forces of dislocations via the force constant matrix of the material's perfect lattice. We use it to study a model of a screw dislocation in bcc tungsten, where we show the existence of two distinct Kanzaki force terms: the slip Kanzaki forces, which we show directly correspond with the BK forces implied by a Volterra dislocation; and the core Kanzaki forces, which are computed from the relaxed dislocation structure, and serve to model all core effects not captured by the Volterra dislocation. We build a multipolar field expansion of both the core and the slip Kanzaki forces, showing that the dislocation core is agreeable to correction via the multipolar field expansion of the core Kanzaki forces. read less J. Verschueren, B. Gurrutxaga-Lerma, D. Balint, A. Sutton, and D. Dini, “Instabilities of High Speed Dislocations.,” Physical review letters. 2018. link Times cited: 19 Abstract: Despite numerous theoretical models and simulation results, … read more Abstract: Despite numerous theoretical models and simulation results, a clear physical picture of dislocations traveling at velocities comparable to the speed of sound in the medium remains elusive. Using two complementary atomistic methods to model uniformly moving screw dislocations, lattice dynamics and molecular dynamics, the existence of mechanical instabilities in the system is shown. These instabilities are found at material-dependent velocities far below the speed of sound. We show that these are the onset of an atomistic kinematic generation mechanism, which ultimately results in an avalanche of further dislocations. This homogeneous nucleation mechanism, observed but never fully explained before, is relevant in moderate and high strain rate phenomena including adiabatic shear banding, dynamic fracture, and shock loading. In principle, these mechanical instabilities do not prevent supersonic motion of dislocations. read less M. Qiu, L. Zhai, J. Cui, B. Fu, M. Li, and Q. Hou, “Diffusion behavior of hydrogen isotopes in tungsten revisited by molecular dynamics simulations,” Chinese Physics B. 2018. link Times cited: 8 T. Swinburne and M. Marinica, “Unsupervised Calculation of Free Energy Barriers in Large Crystalline Systems.,” Physical review letters. 2018. link Times cited: 25 Abstract: The calculation of free energy differences for thermally act… read more Abstract: The calculation of free energy differences for thermally activated mechanisms in the solid state are routinely hindered by the inability to define a set of collective variable functions that accurately describe the mechanism under study. Even when possible, the requirement of descriptors for each mechanism under study prevents implementation of free energy calculations in the growing range of automated material simulation schemes. We provide a solution, deriving a path-based, exact expression for free energy differences in the solid state which does not require a converged reaction pathway, collective variable functions, Gram matrix evaluations, or probability flux-based estimators. The generality and efficiency of our method is demonstrated on a complex transformation of C15 interstitial defects in iron and double kink nucleation on a screw dislocation in tungsten, the latter system consisting of more than 120 000 atoms. Both cases exhibit significant anharmonicity under experimentally relevant temperatures. read less S. Xu, S. Chavoshi, and Y. Su, “Deformation Mechanisms in Nanotwinned Tungsten Nanopillars: Effects of Coherent Twin Boundary Spacing,” physica status solidi (RRL) – Rapid Research Letters. 2018. link Times cited: 20 Abstract: Nano‐scale coherent twin boundaries (CTBs) significantly alt… read more Abstract: Nano‐scale coherent twin boundaries (CTBs) significantly alter the mechanical and electrical properties of metallic materials. Despite a number of studies of the nanotwinned nanopillars in face‐centered cubic metals, investigations of them in body‐centered cubic (BCC) systems are rare. In this Letter, we explore the uniaxial deformation mechanisms of BCC tungsten nanopillars containing nano‐scale {112} CTBs using molecular dynamics (MD) simulations. Our work reveals a novel tension–compression asymmetric stress–strain response and deformation behavior, in conjunction with the effects of CTB spacing. With a relatively large CTB spacing, the plastic deformation in nanotwinned nanopillars is mainly controlled by dislocation nucleation from surface/CTB intersections, gliding on distant and adjacent slip planes under tensile and compressive loading, respectively; as a result, the tensile yield stress is almost invariant with respect to the CTB spacing, while the compressive yield stress increases with a decreasing CTB spacing. As the CTB spacing reduces to 1 nm, detwinning, exhibited by annihilation of {112} twin layers as a result of partial dislocations gliding on CTBs, is observed in both tension and compression; at higher strains, however, {111} incoherent twin boundaries, whose resistance to cracking contributes to strain hardening, are formed under tensile loading but not under compressive loading. read less 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 more Abstract: 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 S. Xu, Y. Su, D. Chen, and L. Li, “An atomistic study of the deformation behavior of tungsten nanowires,” Applied Physics A. 2017. link Times cited: 17 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 more Abstract: 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 S. Xu, J. Startt, T. Payne, C. Deo, and D. McDowell, “Size-dependent plastic deformation of twinned nanopillars in body-centered cubic tungsten,” Journal of Applied Physics. 2017. link Times cited: 31 Abstract: Compared with face-centered cubic metals, twinned nanopillar… read more Abstract: Compared with face-centered cubic metals, twinned nanopillars in body-centered cubic (BCC) systems are much less explored partly due to the more complicated plastic deformation behavior and a lack of reliable interatomic potentials for the latter. In this paper, the fault energies predicted by two semi-empirical interatomic potentials in BCC tungsten (W) are first benchmarked against density functional theory calculations. Then, the more accurate potential is employed in large scale molecular dynamics simulations of tensile and compressive loading of twinned nanopillars in BCC W with different cross sectional shapes and sizes. A single crystal, a twinned crystal, and single crystalline nanopillars are also studied as references. Analyses of the stress-strain response and defect nucleation reveal a strong tension-compression asymmetry and a weak pillar size dependence in the yield strength. Under both tensile and compressive loading, plastic deformation in the twinned nanopillars is dominated by dislocatio... read less A. Backer et al., “Primary damage in tungsten using the binary collision approximation, molecular dynamic simulations and the density functional theory,” Physica Scripta. 2016. link Times cited: 17 Abstract: The damage produced by primary knock-on atoms (PKA) in W has… read more Abstract: The damage produced by primary knock-on atoms (PKA) in W has been investigated from the threshold displacement energy (TDE) where it produces one self interstitial atom–vacancy pair to larger energies, up to 100 keV, where a large molten volume is formed. The TDE has been determined in different crystal directions using the Born–Oppenheimer density functional molecular dynamics (DFT-MD). A significant difference has been observed without and with the semi-core electrons. Classical MD has been used with two different empirical potentials characterized as ‘soft’ and ‘hard’ to obtain statistics on TDEs. Cascades of larger energy have been calculated, with these potentials, using a model that accounts for electronic losses (Sand et al 2013 Europhys. Lett. 103 46003). Two other sets of cascades have been produced using the binary collision approximation (BCA): a Monte Carlo BCA using SDTrimSP (Eckstein et al 2011 SDTrimSP: Version 5.00. Report IPP 12/8) (similar to SRIM www.srim.org) and MARLOWE (RSICC Home Page. (https://rsicc.ornl.gov/codes/psr/psr1/psr-137.html) (accessed May, 2014)). The comparison of these sets of cascades gave a recombination distance equal to 12 Å which is significantly larger from the one we reported in Hou et al (2010 J. Nucl. Mater. 403 89) because, here, we used bulk cascades rather than surface cascades which produce more defects (Stoller 2002 J. Nucl. Mater. 307 935, Nordlund et al 1999 Nature 398 49). Investigations on the defect clustering aspect showed that the difference between BCA and MD cascades is considerably reduced after the annealing of the cascade debris at 473 K using our Object Kinetic Monte Carlo model, LAKIMOCA (Domain et al 2004 J. Nucl. Mater. 335 121). read less D. Cereceda et al., “Linking atomistic, kinetic Monte Carlo and crystal plasticity simulations of single‐crystal tungsten strength,” GAMM‐Mitteilungen. 2015. link Times cited: 12 Abstract: Understanding and improving the mechanical properties of tun… read more Abstract: Understanding and improving the mechanical properties of tungsten is a critical task for the materials fusion energy program. The plastic behavior in body‐centered cubic (bcc) metals like tungsten is governed primarily by screw dislocations on the atomic scale and by ensembles and interactions of dislocations at larger scales. Modeling this behavior requires the application of methods capable of resolving each relevant scale. At the small scale, atomistic methods are used to study single dislocation properties, while at the coarse‐scale, continuum models are used to cover the interactions between dislocations. In this work we present a multiscale model that comprises atomistic, kinetic Monte Carlo (kMC) and continuum‐level crystal plasticity (CP) calculations. The function relating dislocation velocity to applied stress and temperature is obtained from the kMC model and it is used as the main source of constitutive information into a dislocation‐based CP framework. The complete model is used to perform material point simulations of single‐crystal tungsten strength. We explore the entire crystallographic orientation space of the standard triangle. Non‐Schmid effects are inlcuded in the model by considering the twinning‐antitwinning (T/AT) asymmetry in the kMC calculations. We consider the importance of 〈111〉{110} and 〈111〉{112} slip systems in the homologous temperature range from 0.08Tm to 0.33Tm, where Tm =3680 K is the melting point in tungsten. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) read less A. Stukowski, D. Cereceda, T. Swinburne, and J. Marian, “Thermally-activated non-Schmid glide of screw dislocations in W using atomistically-informed kinetic Monte Carlo simulations,” International Journal of Plasticity. 2014. link Times cited: 82 S. Xu, “MODELING PLASTIC DEFORMATION OF NANO/SUBMICRON-SIZED TUNGSTEN PILLARS UNDER COMPRESSION: A COARSE-GRAINED ATOMISTIC APPROACH,” International Journal for Multiscale Computational Engineering. 2018. link Times cited: 8 Abstract: In this work, coarse-grained atomistic simulations via the c… read more Abstract: In this work, coarse-grained atomistic simulations via the concurrent atomistic-continuum (CAC) method are performed to investigate compressive deformation of nano-/submicron-sized pillars in body-centered cubic (BCC) tungsten. Two models with different surface roughness are considered. All pillars have the same height-to-diameter aspect ratio of 3, with the diameter ranging from 27.35 to 165.34 nm; as a result, the largest simulation cell contains 291,488 finite elements, compared to otherwise ≈ 687.82 million atoms in an equivalent full atomistic model. Results show that (i) a larger surface roughness leads to a lower yield stress and (ii) the yield stress of pillars with a large surface roughness scales nearly linearly with the diameter while that of pillars with smooth surfaces scales exponentially with the diameter, the latter of which agrees with experiments. The differences in the yield stress between the two models are attributed to their different plastic deformation mechanisms: in the case of large surface roughness, dislocation nucleation is largely localized near the ends of the pillars; and in pillars with smooth surfaces, dislocation avalanches in a more homogeneous manner are observed. This work, which is the first attempt to simulate BCC systems using the CAC method, highlights the significance of the surface roughness in uniaxial deformation of nano-/submicropillars. read less S. Xu and S. Chavoshi, “Uniaxial deformation of nanotwinned nanotubes in body-centered cubic tungsten,” Current Applied Physics. 2018. link Times cited: 20 Q.-D. Meng, L. Niu, Y. Zhang, and G. Lu, “Molecular dynamics simulations of temperature effect on tungsten sputtering yields under helium bombardment,” Science China Physics, Mechanics & Astronomy. 2017. link Times cited: 7 A. M. Kazakov et al., “Interaction of edge dislocations with voids in tungsten,” Tungsten. 2023. link Times cited: 0 J. Shi et al., “Atomistic insights into the influence of hydrogen on crack propagation in tungsten,” Fusion Engineering and Design. 2023. link Times cited: 0 H. Park, S. Moon, and K. Kang, “The effect of atomic hydrogen on the behavior of a single dislocation of 〈111〉112 in bcc tungsten: atomistic study,” Journal of Nuclear Materials. 2023. link Times cited: 0 Q. Liu et al., “Grain size dependence of grain rotation under high pressure and high temperature,” Journal of Applied Physics. 2023. link Times cited: 0 Abstract: Grain rotation caused by the movement of dislocations is a d… read more Abstract: Grain rotation caused by the movement of dislocations is a determinant factor for the mechanical behavior of metals. In general, the grain rotation may be mediated by grain boundary dislocations (GB-dis) and intragranular dislocations (In-dis), which are closely associated with grain size. Few works have investigated how grain size depends on grain rotation, and the competitive mechanism between GB-dis and In-dis remains unclear. The present work investigates the structural evolution and deformation of coarse-grained tungsten under high pressure. The results show that under high pressure, the nano-sized grains preferentially rotate with dislocation climbing in GBs. Under high pressure, In-dis migrate faster across coarse grains and are absorbed by GBs on the other side, resulting in grain rotation. Elevated temperature also facilitates the migration of In-dis to arrive GBs where they can be absorbed by GBs, thus promoting grain rotation. The theoretical results show that grain rotation occurs easily under high pressure and high temperature. With increasing grain size, the stress-induced rotation mechanism goes from being dominated by GB-dis to being dominated by In-dis migration. The competitive relationship between GB-dis and In-dis during grain rotation is elaborated, providing a new strategy for designing materials under high pressure. read less P. Jiang et al., “Development of U-Zr-Xe ternary interatomic potentials appropriate for simulation of defect and Xe behaviors in U-Zr system,” Journal of Nuclear Materials. 2023. link Times cited: 0 A. D. Backer et al., “Readdressing nanocavity diffusion in tungsten,” Frontiers in Nuclear Engineering. 2023. link Times cited: 0 Abstract: In nuclear fusion (ITER and the future DEMO), those componen… read more Abstract: In nuclear fusion (ITER and the future DEMO), those components that face the plasma are exposed to high temperature and irradiation which, in the long term, modifies their thermal and mechanical properties and tritium retention. Tungsten is a candidate material and is the subject of many studies of microstructure evolution under various irradiation and temperature conditions. One milestone is the characterization of its defect properties. We here readdress the diffusion of nanocavities on broad ranges of size and temperature and compare it with dissociation, a competing process during nanocavity growth. First, at the atomic scale, we used molecular dynamics to explore the variety of elementary events involved in the nanocavity diffusion. Second, an experimental study of ion-irradiated samples, annealed at different temperatures up to 1,773 K, revealed the creation and growth of nanocavities on transmission electron microscopy images. Third, we performed multi-objective optimization of the nanocavity diffusion input of our object kinetic Monte Carlo model to reproduce the experimental results. Finally, we applied a sensitivity analysis of the main inputs of our model developed for these particular conditions—the source term which combines two cascade databases and the impurities whose interaction with the defects is characterised with a supplemented database of density functional theory calculations. Three domains of nanocavity size were observed. The first is the small vacancy clusters, for which atomistic calculations are possible and dissociation is negligible. The second is the small nanocavities, for which we provide new diffusion data and where a competition with the dissociation can take place. The third domain is the large nanocavities, for which, in any case, the dissociation prevents their existence above 1,500 K in the absence of a stabilizing interface. read less D. Kireev, V. Pelenovich, B. Yang, A. Nazarov, and A. E. Ieshkin, “Inelastic processes under gas cluster ion bombardment of metals,” Vacuum. 2023. link Times cited: 0 X. Zheng et al., “Ab initio calculations and empirical potential assessments of the energy and structure of symmetric tilt grain boundaries in tungsten,” Computational Materials Science. 2023. link Times cited: 1 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 X. Peng, N. Mathew, I. Beyerlein, E. Martínez, and A. Hunter, “A combined kinetic Monte Carlo and phase field approach to model thermally activated dislocation motion,” Computational Materials Science. 2023. link Times cited: 0 S. Starikov, A. Abbass, R. Drautz, and M. Mrovec, “Disordering complexion transition of grain boundaries in bcc metals: Insights from atomistic simulations,” Acta Materialia. 2023. link Times cited: 0 R. Ji, T. Phan, Y. Chen, D. McDowell, and L. Xiong, “An Atomistic-to-Microscale Characterization of the Kink-controlled Dislocation Dynamics in BCC Metals through Finite-Temperature Coarse-grained Atomistic Simulations,” Acta Materialia. 2023. link Times cited: 2 J. Xiao et al., “Origin of Deformation Twinning in bcc Tungsten and Molybdenum.,” Physical review letters. 2023. link Times cited: 0 Abstract: Twinning is profuse in bcc transition metals (TMs) except bu… read more Abstract: Twinning is profuse in bcc transition metals (TMs) except bulk W and Mo. However, W and Mo nanocrystals surprisingly exhibit twinning during room temperature compression, which is completely unexpected as established nucleation mechanisms are not viable in them. Here, we reveal the physical origin of deformation twinning in W and Mo. We employ density functional theory (DFT) and a reduced-constraint slip method to compute the stress-dependent generalized stacking fault enthalpy (GSFH), the thermodynamic quantity to be minimized under constant loading. The simple slipped structures and GSFH lines show that compressive stresses stabilize a two-layer twin embryo, which can grow rapidly via twinning disconnections with negligible energy barriers. Direct atomistic simulations unveil the explicit twinning path in agreement with the DFT GSFH lines. Twinning is thus the preferred deformation mechanism in W and Mo when shear stresses are coupled with high compressive stresses. Furthermore, twinnability can be related to the elastic constants of a stacking fault phase (SFP). The hcp phase may serve as a candidate SFP for the {112}⟨1[over ¯]1[over ¯]1⟩ twinning system in bcc TMs and alloys, which is coincident with the {111}⟨112[over ¯]⟩ twinning in fcc structures. read less X.-Y. Wang et al., “Deep neural network potential for simulating hydrogen blistering in tungsten,” Physical Review Materials. 2023. link Times cited: 0 F. Shuang, R. Ji, L. Xiong, and W. Gao, “Effect of periodic image interactions on kink pair activation of screw dislocation,” Computational Materials Science. 2023. link Times cited: 0 Y. Li and W. Qiang, “Dynamic heterogeneity of atomic transport in a body-centered cubic WTaVCr non-equiatomic high-entropy alloy,” Journal of Nuclear Materials. 2023. link Times cited: 0 P. Ma, D. Mason, S. V. Boxel, and S. Dudarev, “Athermal evolution of nanocrystalline tungsten driven by irradiation,” Journal of Nuclear Materials. 2023. link Times cited: 1 C.-J. Ding et al., “A deep learning interatomic potential suitable for simulating radiation damage in bulk tungsten,” Tungsten. 2023. link Times cited: 0 S. Lyu, W. Li, Y. Xia, Y. Chen, and A. Ngan, “Effects of chemical randomness on strength contributors and dislocation behaviors in a bcc multiprincipal element alloy,” Physical Review Materials. 2023. link Times cited: 0 B. Sboui, D. Rodney, and P.-A. Geslin, “Elastic modelling of lattice distortions in concentrated random alloys,” Acta Materialia. 2023. link Times cited: 1 C. Cupak et al., “Sputter yield reduction and fluence stability of numerically optimized nanocolumnar tungsten surfaces,” Physical Review Materials. 2023. link Times cited: 1 J. Qi, C. Oberdorfer, E. Marquis, and W. Windl, “Origin of enhanced zone lines in field evaporation maps,” Scripta Materialia. 2023. link Times cited: 1 R. Zheng, W. Xuan, J. Xie, S. Chen, L. Yang, and L. Zhang, “The Evolution of Structural Defects under Irradiation in W by Molecular Dynamics Simulation,” Materials. 2023. link Times cited: 0 Abstract: Tungsten (W) can be used in plasma-facing components in a fu… read more Abstract: Tungsten (W) can be used in plasma-facing components in a fusion reactor because of its excellent radiation resistance. Some studies have found that nanocrystalline metals with a high density of grain boundary show a higher ability to resist radiation damage compared to conventional coarse-grained materials. However, the interaction mechanism between grain boundary and defect is still unclear. In the present study, molecular dynamics simulations were carried out to explore the difference of defect evolution in single-crystal and bicrystal W, while the effects of temperature and the energy of the primary knocked atom (PKA) were taken into account. The irradiation process was simulated at the temperature range of 300 to 1500 K, and the PKA energy varied from 1 to 15 keV. The results show that the generation of defects is more sensitive to the energy of PKA than temperature; the number of defects increases at the thermal spike stage with the increase of the PKA energy, but the correlation with temperature is not strong. The presence of the grain boundary prevented the recombination of interstitial atoms and vacancies during the collision cascades, and the vacancies were more likely to form large clusters than interstitial atoms in the bicrystal models. This can be ascribed to the strong segregation tendency of the interstitial atoms to grain boundaries. The simulations provide useful information for understanding the role of grain boundaries in the evolution of irradiated structural defects. read less 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 more Abstract: 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 F. J. Domínguez-Gutiérrez et al., “Nanoindentation of tungsten: From interatomic potentials to dislocation plasticity mechanisms,” Physical Review Materials. 2023. link Times cited: 1 A. Nazarov et al., “On the angular distributions of atoms sputtered by gas cluster ion beam,” Vacuum. 2023. link Times cited: 2 “The structure and energy of symmetric tilt grain boundaries in tungsten,” Journal of Nuclear Materials. 2023. link Times cited: 1 C. Ji, J. Hu, Z. Zhuang, and Y. Cui, “Atomistically-informed hardening and kinetics models of helium bubble in irradiated tungsten,” International Journal of Plasticity. 2023. link Times cited: 2 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 C. Petersson, A. Fredriksson, S. Melin, A. Ahadi, and P. Hansson, “A molecular dynamics study on the influence of vacancies and interstitial helium on mechanical properties of tungsten,” Journal of Nuclear Materials. 2023. link Times cited: 0 A. Zhong, C. Lapointe, A. Goryaeva, J. Baima, M. Athènes, and M. Marinica, “Anharmonic thermo-elasticity of tungsten from accelerated Bayesian adaptive biasing force calculations with data-driven force fields,” Physical Review Materials. 2023. link Times cited: 1 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 A. Lopez-Cazalilla, J. Jussila, K. Nordlund, and F. Granberg, “Effect of surface morphology on Tungsten sputtering yields,” Computational Materials Science. 2023. link Times cited: 2 C. Hu et al., “Self-Layering of (Ti,Al)N by Interface-Directed Spinodal Decomposition of (Ti,Al)N/Tin Multilayers: First-Principles and Experimental Investigations,” SSRN Electronic Journal. 2022. link Times cited: 5 P. Hatton, M. J. Hatton, D. Perez, and B. Uberuaga, “The importance of long-timescale simulations for driven systems: An example of He bubble growth at a W GB,” MRS Communications. 2022. link Times cited: 0 Abstract: Accelerated Molecular Dynamics (AMD) is used to study comple… read more Abstract: Accelerated Molecular Dynamics (AMD) is used to study complex systems under realistic conditions by extending the timescales accessible by Molecular Dynamics. However, some studies rely instead on driving atomic systems harder with higher temperature, faster growth, etc. We study He bubble growth at a W grain boundary as an illustration of harnessing AMD methods to avoid consequences of over-driving the system. The growth mechanisms observed for a He bubble grown under realistic conditions are compared to bubbles-grown orders of magnitude faster, at rates typical of conventional molecular dynamics simulations. We find that progressive growth mechanisms and bubble structures depend on the rate at which the bubble is grown providing further evidence that care must be taken when simulating the dynamics of driven systems such as this one. Graphical abstract read less R. Zheng, L. Yang, and L. Zhang, “Grain Boundary Migration as a Self-Healing Mechanism of Tungsten at High Temperature,” Metals. 2022. link Times cited: 2 Abstract: The tungsten components in nuclear fusion reactors need to w… read more Abstract: The tungsten components in nuclear fusion reactors need to withstand the radiation cascade damage caused by the neutron bombardment of high temperature and high throughput fusion reaction during service. These damages are mainly present as a high concentration of point defects and clusters, which lead to a series of problems such as irradiation-hardening and decreased thermal conductivity of materials. In this study, molecular dynamics simulations are carried out to study the dynamic interaction between grain boundaries and the void in tungsten at high temperatures (T > 2500 K). Different interatomic potentials of W were tested, and the most appropriate one was selected by the thermodynamic and kinetic properties of W. Simulation results show that the dynamic migration of grain boundary can absorb the void, but the absorption efficiency of grain boundaries is sensitive to their structural characteristics, where the high-angle GBs are more absorptive to the void than the low-angle GBs. It is found that the void absorption cannot be completely attributed to the thermal diffusion mechanism during the GB-void interaction; the dynamic migration of high-angle GBs can significantly accelerate the void absorption. This study reveals a GB migration-induced self-healing mechanism of W at high temperatures. read less R. Ji, T. Phan, Y. Chen, D. McDowell, and L. Xiong, “A finite-temperature coarse-grained atomistic approach for understanding the kink-controlled dynamics of micrometer-long dislocations in high-Peierls-barrier materials,” MRS Communications. 2022. link Times cited: 6 Abstract: We present a phonon dynamics-based finite-temperature coarse… read more Abstract: We present a phonon dynamics-based finite-temperature coarse-grained (FT-CG) atomistic approach for characterizing the kink-controlled dislocation dynamics in high-Peierls-barrier materials. The applicability of it is demonstrated through simulating the motion of a ~ 3 µm-long dislocation in a bcc iron sample containing ~ 230 million atoms. Cross-kink and debris are found on a µm-long dislocation at a lower stress than that on a nm-long dislocation. They are largely promoted by high-frequency/short-wavelength phonons. FT-CG is shown to be a first model of its kind that can predict the mobility of a µm-long dislocation without smearing out the atomic-level kink dynamics on it. Graphical abstract read less J. Hu, X. Liu, and Y. Wei, “Head-on impact of metal microparticles: aggregation or separation?,” International Journal of Impact Engineering. 2022. link Times cited: 1 C. Savvidi, G. Evangelakis, and V. Pontikis, “Boundary conditions for molecular simulations of isolated elastic defects. Case study: The ⟨111⟩ screw dislocation in bcc W,” Journal of Applied Physics. 2022. link Times cited: 0 Abstract: A new set of boundary conditions is proposed for molecular s… read more Abstract: A new set of boundary conditions is proposed for molecular simulations of isolated elastic defects such as dislocations and cracks. The case study of the [Formula: see text] screw dislocation in body centered cubic (bcc) tungsten, modeled via a phenomenological, n-body cohesion functional, serves validating the new boundary conditions by computing structural properties of this defect and comparing these with results from the literature. Lowest energy configurations of the dislocated crystal have been obtained by molecular statics incorporating the new boundary conditions. The associated displacement and energy landscapes reveal conformal to the predictions of the elastic theory for a screw dislocation embedded in an infinitely extended crystal. In particular, no energy gradients and positional mismatch of atoms are found at the terminations of the computational box, validating thereby the new boundary conditions. Furthermore, it is shown that the structure, the spatial extension, and the excess energy of the two possible core polarizations of this dislocation compare consistently with existing findings for this and other bcc metals. Close to the dislocation line, energy minimization triggers the emergence of anelastic edge displacements extending over distances unexpectedly much larger than the dislocation core radius. Therefore, the conclusion is reached that in molecular simulations, the transverse to the dislocation line dimensions of the atomistic model should be taken considerably larger than it is accustomed. Perspectives opened by the present work are briefly discussed. read less A. Lopez-Cazalilla et al., “Comparative study regarding the sputtering yield of nanocolumnar tungsten surfaces under Ar+ irradiation,” Physical Review Materials. 2022. link Times cited: 5 Y. Hu, P. Huang, and F. Wang, “Graphene distribution and structural integrity dependent irradiation resistance of graphene/tungsten composites,” Materials Today Communications. 2022. link Times cited: 4 F. Valencia, R. Ortega, R. González, E. Bringa, M. Kiwi, and C. Ruestes, “Nanoindentation of nanoporous tungsten: A molecular dynamics approach,” Computational Materials Science. 2022. link Times cited: 6 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 N. Mathew, D. Perez, W. Suk, B. Uberuaga, and E. Martínez, “Interstitial hydrogen enhances the mobility of some grain boundaries in tungsten,” Nuclear Fusion. 2022. link Times cited: 3 Abstract: Segregation of interstitials at a grain boundary (GB) is kno… read more Abstract: Segregation of interstitials at a grain boundary (GB) is known to generally lower its mobility. This phenomenon, called ‘solute-drag’, has important ramifications on the process of recrystallization and microstructural evolution. In this manuscript, we present predictions from molecular dynamics (MD) simulations which demonstrate that interstitial hydrogen in tungsten can in fact increase the mobility of some GBs which exhibit shear coupling. Assuming a disconnection-based mechanism, activation energies and pre-factors for disconnection nucleation are predicted from simulations of shear-coupled motion. In GBs where enhanced mobility is predicted, interstitial H reduces both the activation energy and the pre-factor for disconnection nucleation, thus effectively increasing the mobility. For GBs with diminished mobility, MD predicts that presence of interstitial H reduces the pre-factor and, in some cases, increases the activation energy. The reduction in the activation energy inferred from MD simulations are confirmed by nudged elastic band calculations. Temperature-dependent structural transitions are observed for some GBs, and the effect of interstitial H is found to change with the changes in structure. The effect of interstitial H is predicted to be complex and highly variable, providing some plausible explanations for experimental observations on the recrystallization of tungsten in presence of H-loaded plasma. read less P. Hiremath, S. Melin, E. Bitzek, and P. Olsson, “Effects of interatomic potential on fracture behaviour in single- and bicrystalline tungsten,” Computational Materials Science. 2022. link Times cited: 14 X. Li et al., “Towards the dependence of radiation damage on the grain boundary character and grain size in tungsten: A combined study of molecular statics and rate theory,” Journal of Nuclear Materials. 2022. link Times cited: 8 M. Zhou, B. Fu, Q. Hou, L. Wu, and R. Pan, “Determining the diffusion behavior of point defects in zirconium by a multiscale modelling approach,” Journal of Nuclear Materials. 2022. link Times cited: 3 R. Murzaev, A. Y. Morkina, and I. I. Tuvalev, “Dynamics of delocalized vibrational modes in bcc W: impact of interatomic potential,” Saratov Fall Meeting. 2022. link Times cited: 0 Abstract: In the bcc W, the simulation of oscillations was carried out… read more Abstract: In the bcc W, the simulation of oscillations was carried out according to the patterns of nonlinear delocalized vibrational modes - exact solutions of the equations of motion of atoms, the geometry of which is determined by the symmetry of the lattice. Two-dimensional cases of vibrations in one of the close-packed planes and three-dimensional cases, where the motions of atoms have three components in space, were considered. The amplitude-frequency characteristics (AFC) of these modes were calculated for several interatomic potentials available in the LAMMPS library. read less 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 more Abstract: 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 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 more Abstract: 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 S. Saxena, M. Spinola, P. Gupta, and D. Kochmann, “A fast atomistic approach to finite-temperature surface elasticity of crystalline solids,” Computational Materials Science. 2022. link Times cited: 1 L. Li et al., “Atomic Simulations of the Interaction between a Dislocation Loop and Vacancy-Type Defects in Tungsten,” Metals. 2022. link Times cited: 3 Abstract: Tungsten (W) is considered to be the most promising plasma-f… read more Abstract: Tungsten (W) is considered to be the most promising plasma-facing material in fusion reactors. During their service, severe irradiation conditions create plenty of point defects in W, which can significantly degrade their performance. In this work, we first employ the molecular static simulations to investigate the interaction between a 1/2[111] dislocation loop and a vacancy-type defect including a vacancy, di-vacancy, and vacancy cluster in W. The distributions of the binding energies of a 1/2[111] interstitial and vacancy dislocation loop to a vacancy along different directions at 0 K are obtained, which are validated by using the elasticity theory. The calculated distributions of the binding energies of a 1/2[111] interstitial dislocation loop to a di-vacancy and a vacancy cluster, showing a similar behavior to the case of a vacancy. Furthermore, we use the molecular dynamics simulation to study the effect of a vacancy cluster on the mobility of the 1/2[111] interstitial dislocation loop. The interaction is closely related to the temperature and their relative positions. A vacancy cluster can attract the 1/2[111] interstitial dislocation loop and pin it at low temperatures. At high temperatures, the 1/2[111] interstitial dislocation loop can move randomly. These results will help us to understand the essence of the interaction behaviors between the dislocation loop and a vacancy-type defect and provide necessary parameters for mesoscopic scale simulations. read less L. Ma and R. Aghababaei, “On the Effect of Adhesive Strength and Scratching Depth on Material Transfer During Nanoscale Scratching,” Tribology Letters. 2022. link Times cited: 5 L. Yang, Y.-X. Shen, S. Mi, J. Fan, and H. Gong, “Phase stability and mechanical property of W–Cu solid solutions from a newly derived W–Cu potential,” Physica B: Condensed Matter. 2022. link Times cited: 5 A. Fraile, P. Dwivedi, G. Bonny, and T. Polcar, “Analysis of hypervelocity impacts: the tungsten case,” Nuclear Fusion. 2021. link Times cited: 3 Abstract: The atomistic mechanisms of damage initiation during high ve… read more Abstract: The atomistic mechanisms of damage initiation during high velocity (v up to 9 km s−1, kinetic energies up to 200 keV) impacts of W projectiles on a W surface have been investigated using parallel molecular-dynamics simulations involving large samples (up to 40 million atoms). Various aspects of the high velocity impacts, where the projectile and part of the target material undergo massive plastic deformation, breakup, melting, and vaporization, are analyzed. Different stages of the penetration process have been identified through a detailed examination of implantation, crater size and volume, sputtered atoms, and dislocations created by the impacts. The crater volume increases linearly with the kinetic energy for a given impactor; and the total dislocation length (TDL) increases with the kinetic energy but depends on the size of the impactor. We found that the TDL does not depend on the used interatomic potential. The results are rationalized based on the physical properties of bcc W. read less E. Martínez et al., “Thermal gradient effect on helium and self-interstitial transport in tungsten,” Journal of Applied Physics. 2021. link Times cited: 2 O. Lindblom, T. Ahlgren, and K. Heinola, “Molecular dynamics simulations of hydrogen isotope exchange in tungsten vacancies,” Nuclear Materials and Energy. 2021. link Times cited: 3 Y. Xie, K. Shibata, and T. Miozguchi, “A brute-force code searching for cell of non-identical displacement for CSL grain boundaries and interfaces,” Computer Physics Communications. 2021. link Times cited: 4 H. He, S. Ma, and S. Wang, “Molecular dynamics investigation on tilt grain boundary energies of beta-titanium and tungsten at high temperature,” Materials Research Express. 2021. link Times cited: 2 Abstract: The grain boundary energies (GBEs) of symmetric tilt grain b… read more Abstract: The grain boundary energies (GBEs) of symmetric tilt grain boundaries (STGBs) and asymmetric tilt grain boundaries (ATGBs) for W at 0 and 2400 K and β-Ti at 1300 K were calculated by means of molecular statics and dynamics simulations to investigate the effects of temperature on GBE and the relationships between GBEs and grain boundary (GB) planes. Generally, the variation trends of GBE with the tilt angle are similar for the three cases, when the tilt axis is specified. It is of course that these similarities result from their similar GB microstructures in most cases. However, the variation trends of GBE with tilt angle are somewhat different between β-Ti at 1300 K and W at 2400 K for STGBs with <100> and <110> tilt axes. This difference mainly stems from the following two reasons: firstly, the GB microstructures of W at 2400 K and β-Ti at 1300 K are different for some STGBs; secondly, the atoms at the STGB of β-Ti at 1300 K tend to evolve into the local ω- or α-like structures distributed at the STGB for some STGBs with <110> tilt axis, which makes the corresponding STGBs more stable, thereby decreasing the GBEs. Furthermore, a geometric parameter θ, the angle between the misorientation axis and the GB plane, was defined to explore the relationships between GBEs and GB planes. It was found that the relationships between GBEs and GB planes can be described by some simple functions of sin(θ) for the GBs with definite lattice misorientation, which can well explain and predict the preferred GB planes for the GBs having the same lattice misorientation. Our calculations not only extend the investigation of GBs to higher temperature, but also deepen the understanding on the temperature contributions to the microstructure evolution at GBs and on the relationships between GBEs and possible geometric parameters. read less Y. Wang et al., “Prediction of vacancy formation energies at tungsten grain boundaries from local structure via machine learning method,” Journal of Nuclear Materials. 2021. link Times cited: 6 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 more Abstract: 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 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 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 Y. Qian, M. Gilbert, L. Dezerald, and D. Cereceda, “Using first-principles calculations to predict the mechanical properties of transmuting tungsten under first wall fusion power-plant conditions,” Journal of Physics: Condensed Matter. 2021. link Times cited: 4 Abstract: Tungsten and tungsten alloys are being considered as leading… read more Abstract: Tungsten and tungsten alloys are being considered as leading candidates for structural and functional materials in future fusion energy devices. The most attractive properties of tungsten for the design of magnetic and inertial fusion energy reactors are its high melting point, high thermal conductivity, low sputtering yield and low long-term disposal radioactive footprint. Yet, despite these relevant features, tungsten also presents a very low fracture toughness, mostly associated with inter-granular failure and bulk plasticity, that limits its applications. Significant neutron-induced transmutation happens in these tungsten components during nuclear fusion reactions, creating transmutant elements including Re, Os and Ta. Density functional theory (DFT) calculations that allow the calculation of defect and solute energetics are critical to better understand the behavior and evolution of tungsten-based materials in a fusion energy environment. In this study, we present a novel computational approach to perform DFT calculations on transmuting materials. In particular, we predict elastic and plastic mechanical properties (such as bulk modulus, shear modulus, ductility parameter, etc) on a variety of W–X compositions that result when pure tungsten is exposed to the EU-DEMO fusion first wall conditions for ten years. read less 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 P. Wang, Q. Cao, S. Liu, and Q. Peng, “Fragility under shocking: molecular dynamics insights into defect evolutions in tungsten lattice,” Tungsten. 2021. link Times cited: 6 X. Wang, S. Xu, W. Jian, X.-G. Li, Y. Su, and I. Beyerlein, “Generalized stacking fault energies and Peierls stresses in refractory body-centered cubic metals from machine learning-based interatomic potentials,” Computational Materials Science. 2021. link Times cited: 30 L. Yang, D. Perez, and B. Wirth, “Stability and mobility of tungsten clusters on tungsten (110) surface: Ab initio and atomistic simulations,” Surface Science. 2021. link Times cited: 3 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 A. Al-Motasem, T. Huminiuc, and T. Polcar, “Factors controlling segregation tendency of solute Ti, Ag and Ta into different symmetrical tilt grain boundaries of tungsten: First-principles and experimental study,” Acta Materialia. 2021. link Times cited: 19 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 Y. Osetsky, “Atomic-scale mechanisms of void strengthening in tungsten,” Tungsten. 2021. link Times cited: 11 W. Zhang et al., “Panorama of ‘fuzz’ growth on tungsten surface under He irradiation,” Applied Surface Science. 2021. link Times cited: 5 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 M. Powers, B. Derby, S. N. Manjunath, and A. Misra, “Hierarchical morphologies in co-sputter deposited thin films,” Physical Review Materials. 2020. link Times cited: 5 X. Zhang, K. Xu, Y. Zhang, Y.-H. Li, S. Jin, and G. Lu, “Equilibrium concentration of hydrogen at tungsten surface,” Journal of Nuclear Materials. 2020. link Times cited: 0 D. Meluzova, P. Babenko, A. Zinoviev, and A. Shergin, “Sputtering of Tungsten by Beryllium and Neon Ions,” Technical Physics Letters. 2020. link Times cited: 0 F.-F. Ma et al., “Collaborative motion of helium and self-interstitial atoms enhanced self-healing efficiency of irradiation-induced defects in tungsten,” Nuclear Fusion. 2020. link Times cited: 2 Abstract: Helium (He) is a typical impurity element and plays a crucia… read more Abstract: Helium (He) is a typical impurity element and plays a crucial role in the microstructural evolution in nuclear materials under irradiation. Here, we systematically investigate the interactions between He and self-interstitial atoms (SIAs) as well as their influences on the kinetic behaviors of SIAs in tungsten (W), using both first-principles and object kinetic Monte Carlo methods. It is found that there are attractive interactions between He and SIAs, which become stronger with the increasing of SIA numbers. Specifically, the He-SIA1 and He-SIA2 complexes adopt a three-dimensional (3D) migration pattern with an effective energy barrier of 0.38 and 0.61 eV, respectively, which is completely different from the 1D migration of SIAs in W (⩽0.033 eV) without He. Such an unexpected collaborative 3D motion of He-SIA complexes increases the probability of vacancy-interstitial recombination and reduces the number of surviving defects. Consequently, our calculations reveal the enhanced effect of He on the self-healing efficiency in W, which is originated from the collaborative 3D motion of He-SIA complexes. The current results can improve our fundamental understanding of the influence of He on the evolution of irradiation defects and have great implications to estimate the performance of W-PFMs in fusion environment. read less K. Schlueter et al., “Absence of a Crystal Direction Regime in which Sputtering Corresponds to Amorphous Material.,” Physical review letters. 2020. link Times cited: 7 Abstract: Erosion of material by energetic ions, i.e., sputtering, is … read more Abstract: Erosion of material by energetic ions, i.e., sputtering, is widely used in industry and research. Using experiments and simulations that, independently of each other, obtain the sputter yield of thousands of individual grains, we demonstrate here that the sputter yield for heavy keV ions on metals changes as a continuous function of the crystal direction. Moreover, we show that polycrystalline metals with randomly oriented grains do not sputter with the same yield as the amorphous material. The key reason for this is attributed to linear collision sequences rather than channeling. read less 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 more Abstract: 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 S. Xu, Y. Su, L. Smith, and I. Beyerlein, “Frank-Read source operation in six body-centered cubic refractory metals,” Journal of The Mechanics and Physics of Solids. 2020. link Times cited: 39 G. Bonny, N. Castin, A. Bakaev, A. Sand, and D. Terentyev, “Effects of cascade-induced dislocation structures on the long-term microstructural evolution in tungsten,” Computational Materials Science. 2020. link Times cited: 11 H. Zhao, X.-guo Zeng, X. Yang, W. Chen, and J. Wu, “Investigation of the temperature effect on the primary radiation damage near the grain boundary in tungsten using Molecular dynamics simulations,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2020. link Times cited: 4 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 more Abstract: 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 R. Alexander et al., “Interatomic potentials for irradiation-induced defects in iron,” Journal of Nuclear Materials. 2020. link Times cited: 13 A. Bondarev, A. Fraile, T. Polcar, and D. Shtansky, “Mechanisms of friction and wear reduction by h-BN nanosheet and spherical W nanoparticle additives to base oil: Experimental study and molecular dynamics simulation,” Tribology International. 2020. link Times cited: 35 S. Xu, X. Fan, C. Gu, Y. Shi, D. J. Singh, and W. Zheng, “First principles and molecular dynamics study of Li wetting and diffusion on W surfaces,” Journal of Nuclear Materials. 2020. link Times cited: 6 J. Wang et al., “Anti-twinning in nanoscale tungsten,” Science Advances. 2020. link Times cited: 51 Abstract: Tungsten nanowires showed an unexpected anti-twinning phenom… read more Abstract: Tungsten nanowires showed an unexpected anti-twinning phenomenon, which is strongly size-dependent. Nanomaterials often surprise us with unexpected phenomena. Here, we report a discovery of the anti-twinning deformation, previously thought impossible, in nanoscale body-centered cubic (BCC) tungsten crystals. By conducting in situ transmission electron microscopy nanomechanical testing, we observed the nucleation and growth of anti-twins in tungsten nanowires with diameters less than about 20 nm. During anti-twinning, a shear displacement of 1/3〈111〉 occurs on every successive {112} plane, in contrast to an opposite shear displacement of 1/6〈1¯1¯1¯〉 by ordinary twinning. This asymmetry in the atomic-scale shear pathway leads to a much higher resistance to anti-twinning than ordinary twinning. However, anti-twinning can become active in nanosized BCC crystals under ultrahigh stresses, due to the limited number of plastic shear carriers in small crystal volumes. Our finding of the anti-twinning phenomenon has implications for harnessing unconventional deformation mechanisms to achieve high mechanical preformation by nanomaterials. read less J. Cui, Z.-J. Zhou, B. Fu, and Q. Hou, “Assessing the influence of electronic effects on molecular dynamics simulations of primary radiation damage in tungsten,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2020. link Times cited: 6 R. Ji, T. Phan, H. Chen, and L. Xiong, “Quantifying the dynamics of dislocation kinks in iron and tungsten through atomistic simulations,” International Journal of Plasticity. 2020. link Times cited: 22 J. Grossi, J. Kohanoff, and E. Bringa, “MeV irradiation of tungsten nanowires: structural modifications,” Materials Research Express. 2020. link Times cited: 3 Abstract: In this work we use the Two Temperature Model coupled to Mol… read more Abstract: In this work we use the Two Temperature Model coupled to Molecular Dynamics (TTM-MD) to study swift heavy ion irradiation of W finite nanowires. Au projectiles are considered with energies ranging from 20 to 50 MeV, which correspond to electronic stopping values less than 20 keV nm−1 in the regime where electronic stopping is larger than nuclear stopping. Nanowires with diameters much smaller than the electron mean free path are considered for two different sizes with an aspect ratio ∼3.7 between length and diameter. Nanowires display radiation-induced surface roughening, sputtering yields and the formation of point defects and di-vacancies. For the smallest size, a hole stays opened in the central part of the wire for S e > 12.6 keV nm−1. W nanofoams, considered as collections of connected nanowires like those simulated here, are expected to behave similarly under irradiation displaying radiation resistance for the electronic stopping range that has been considered. In fact, nanowires larger than tens of nm would be needed for defect accumulation and lack of radiation resistance. read less M. Hodapp and A. Shapeev, “In operando active learning of interatomic interaction during large-scale simulations,” Machine Learning: Science and Technology. 2020. link Times cited: 17 Abstract: A well-known drawback of state-of-the-art machine-learning i… read more Abstract: A well-known drawback of state-of-the-art machine-learning interatomic potentials is their poor ability to extrapolate beyond the training domain. For small-scale problems with tens to hundreds of atoms this can be solved by using active learning which is able to select atomic configurations on which a potential attempts extrapolation and add them to the ab initio-computed training set. In this sense an active learning algorithm can be viewed as an on-the-fly interpolation of an ab initio model. For large-scale problems, possibly involving tens of thousands of atoms, this is not feasible because one cannot afford even a single density functional theory (DFT) computation with such a large number of atoms. This work marks a new milestone toward fully automatic ab initio-accurate large-scale atomistic simulations. We develop an active learning algorithm that identifies local subregions of the simulation region where the potential extrapolates. Then the algorithm constructs periodic configurations out of these local, non-periodic subregions, sufficiently small to be computable with plane-wave DFT codes, in order to obtain accurate ab initio energies. We benchmark our algorithm on the problem of screw dislocation motion in bcc tungsten and show that our algorithm reaches ab initio accuracy, down to typical magnitudes of numerical noise in DFT codes. We show that our algorithm reproduces material properties such as core structure, Peierls barrier, and Peierls stress. This unleashes new capabilities for computational materials science toward applications which have currently been out of scope if approached solely by ab initio methods. read less H. Wang et al., “In-situ hydrogen production and storage in (0 0 2) oriented TiO2 thin films,” Applied Surface Science. 2020. link Times cited: 11 L. Liu et al., “Evaluation of tungsten interatomic potentials for radiation damage simulations,” Tungsten. 2020. link Times cited: 10 F. Shuang et al., “A first study on nanoporous tungsten recording electrodes for deep brain stimulation,” Materials Letters. 2020. link Times cited: 6 E. Ercikan, “MOLECULAR DYNAMICS SIMULATION OF HYDROGEN ISOTOPES TRAPPING ON TUNGSTEN: THE EFFECT OF PRE-IRRADIATION.” 2019. link Times cited: 0 Abstract: To achieving successfully commercial nuclear fusion energy, … read more Abstract: To achieving successfully commercial nuclear fusion energy, fully understanding of the interaction between plasma particles and plasma facing components is one of the essential issues. Tungsten, due to good thermal and mechanical properties such as high thermal conductivity and melting temperature, is one of the most promising candidates. However, the plasma facing components interacting with the extreme environmental conditions such as high temperature and radiation may lead to nanostructure formation, sputtering and erosion that will lead to material degradation. And these deformations may influence not only properties of plasma facing components but also might affect the plasma itself. For example, the contamination of plasma with a few amounts of tungsten, a high Z element, as a result of erosion or sputtering may cause core plasma cooling that results in loss of plasma confinement. Additionally, the retention of hydrogen isotopes, especially tritium, in tungsten is essential issue because of its radioactivity and market value. In this study, deuterium trapping in tungsten is analyzed by molecular dynamics method and the effect of pre-irradiation on trapping is studied. Non-cumulative studies show that the increase in the energy of hydrogen isotopes rises the absorption rate, the initial implantation depth, and the average resting time for initial implantation. Additionally, the effect of implanted deuterium due to pre-irradiation on the hydrogen isotopes trapping is analyzed by combining both cumulative and non-cumulative simulations, and results indicate that while the increase in the pre-irradiation time raises the absorption rate of deuterium with higher energy than 80 eV, it causes a decrease the initial implantation depth and the average resting time for initial implantation because of deuterium-deuterium interactions. Additionally, the deuterium-deuterium interactions may transfer enough energy to implanted deuterium to start a motion which may lead to deeper implantation or escaping from the surface of tungsten. The escaping from surface as a result of deuterium-deuterium interaction could explain the decrease in accumulation rate of deuterium while absorption rate rises. read less B. Li, S. Jin, K. Xu, J. Hao, and X. Shu, “Atomistic simulations of the interactions between the 1/2 〈1 1 1〉 1 1 0 edge dislocations and the intrinsic point defects in tungsten,” Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 2019. link Times cited: 1 S. He, E. Overly, V. Bulatov, J. Marian, and D. Cereceda, “Coupling 2D atomistic information to 3D kink-pair enthalpy models of screw dislocations in bcc metals,” Physical Review Materials. 2019. link Times cited: 6 Abstract: The kink-pair activation enthalpy is a fundamental parameter… read more Abstract: The kink-pair activation enthalpy is a fundamental parameter in the theory of plasticity of body-centered cubic (bcc) metals. It controls the thermally activated motion of screw dislocation at low and intermediate temperatures. While direct atomistic calculations of kink pairs on screw dislocations have reached a high degree of accuracy, they can only be practically performed using semiempirical interatomic force fields, as electronic structure methods have not yet reached the level of efficiency needed to capture the system sizes required to model kink-pair structures. In this context, an alternative approach based on standard three-dimensional elastic models, which are efficient but lack atomic-level information, coupled to a substrate potential that represents the underlying lattice, has been widely applied over the past few years. This class of methods, known as `line-on-substrate' (LOS) models, uses the substrate potential to calculate the lattice contribution to the kink-pair energies. In this work, we introduce the stress dependence of the substrate potential into LOS models to evaluate its impact on kink-pair energies. In addition, we include asymmetric dislocation core energies as an extra descriptor of the dislocation character. This asymmetry is also elevated to the continuum level by adding core energies to the general LOS formulation and used to explain potential energy differences known to exist between left and right kinks in bcc metals. More importantly, by matching the total LOS energies to previously calculated atomistic energies of kink-pair configurations, we issue a rule to establish the value of the so-called core width in nonsingular elasticity theories and reduce its arbitrariness as a mathematical construct. read less J. Cui, M. Li, B. Fu, and Q. Hou, “Molecular dynamics simulations of self-diffusion of adatoms on tungsten surfaces,” Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 2019. link Times cited: 2 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 M. Kotoul et al., “Ab initio aided strain gradient elasticity theory in prediction of nanocomponent fracture,” Mechanics of Materials. 2019. link Times cited: 10 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 K. Kowalczyk-Gajewska and M. Maździarz, “Effective stiffness tensor of nanocrystalline materials of cubic symmetry: The core-shell model and atomistic estimates,” International Journal of Engineering Science. 2019. link Times cited: 5 B. Fu, M. Qiu, J. Cui, M. Li, J. Wang, and Q. Hou, “Trapping and detrapping process of hydrogen in tungsten divacancy: A molecular dynamics study,” Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 2019. link Times cited: 1 C. Yang and L. Qi, “Modified embedded-atom method potential of niobium for studies on mechanical properties,” Computational Materials Science. 2019. link Times cited: 17 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 more Abstract: 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 J. Jussila, F. Granberg, and K. Nordlund, “Effect of random surface orientation on W sputtering yields,” Nuclear Materials and Energy. 2018. link Times cited: 15 L. Yang, Z. Bergstrom, and B. Wirth, “Effect of interatomic potential on the energetics of hydrogen and helium-vacancy complexes in bulk, or near surfaces of tungsten,” Journal of Nuclear Materials. 2018. link Times cited: 17 S. Yi, G. Li, Z. Liu, P. H. Hopchev, and H. Deng, “First-Principles Calculations on the Wettability of Li Atoms on the (111) Surfaces of W and Mo Substrates,” Plasma Physics Reports. 2018. link Times cited: 3 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 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 T. Frolov, Q. Zhu, T. Oppelstrup, J. Marian, and R. Rudd, “Structures and transitions in bcc tungsten grain boundaries and their role in the absorption of point defects,” Acta Materialia. 2018. link Times cited: 48 T. Trusty, S. Xu, and I. Beyerlein, “Atomistic simulations of tungsten nanotubes under uniform tensile loading,” Journal of Applied Physics. 2018. link Times cited: 6 Abstract: Metallic nanotubes (NTs) have gained much attention in recen… read more Abstract: Metallic nanotubes (NTs) have gained much attention in recent years due to their exciting potential to be just as strong or even stronger than their heavier counterparts, nanowires (NWs), with the same outer radius. Unlike NWs, NTs have inner wall diameter and wall thickness parameters that can be engineered to provide advantage in structural materials design. In this work, molecular dynamics is used to quantify the combined effects of NT specific dimensions, outer radius and wall thickness, on the tensile strength of single crystalline tungsten NTs at room temperature. Uniaxial tensile simulations are carried out for three different crystallographic orientations along the NT axis—two known as brittle orientations and one as ductile orientation. For these three orientations, the strength of NTs can be made higher than NWs, for the same outer radius, as the wall thickness decreases. The calculations indicate that even for the brittle orientations, NTs can be engineered to be more ductile by tuning the outer radius and the wall thickness.Metallic nanotubes (NTs) have gained much attention in recent years due to their exciting potential to be just as strong or even stronger than their heavier counterparts, nanowires (NWs), with the same outer radius. Unlike NWs, NTs have inner wall diameter and wall thickness parameters that can be engineered to provide advantage in structural materials design. In this work, molecular dynamics is used to quantify the combined effects of NT specific dimensions, outer radius and wall thickness, on the tensile strength of single crystalline tungsten NTs at room temperature. Uniaxial tensile simulations are carried out for three different crystallographic orientations along the NT axis—two known as brittle orientations and one as ductile orientation. For these three orientations, the strength of NTs can be made higher than NWs, for the same outer radius, as the wall thickness decreases. The calculations indicate that even for the brittle orientations, NTs can be engineered to be more ductile by tuning the oute... read less 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 X. Li, S. Schönecker, W. Li, L. Varga, D. Irving, and L. Vitos, “Tensile and shear loading of four fcc high-entropy alloys : A first-principles study,” Physical Review B. 2018. link Times cited: 24 Abstract: Ab initio density-functional calculations are used to invest… read more Abstract: Ab initio density-functional calculations are used to investigate the response of four face-centered-cubic (fcc) high-entropy alloys (HEAs) to tensile and shear loading. The ideal tensile and shear ... read less G. Bonny, N. Castin, A. Bakaev, and D. Terentyev, “Kinetic Monte Carlo model for 1-D migration in a field of strong traps: Application to self-interstitial clusters in W-Re alloys,” Computational Materials Science. 2018. link Times cited: 13 X.-yan Li et al., “On the possibility of universal interstitial emission induced annihilation in metallic nanostructures,” Journal of Nuclear Materials. 2018. link Times cited: 9 S. Katnagallu et al., “Impact of local electrostatic field rearrangement on field ionization,” Journal of Physics D: Applied Physics. 2018. link Times cited: 22 Abstract: Field ion microscopy allows for direct imaging of surfaces w… read more Abstract: Field ion microscopy allows for direct imaging of surfaces with true atomic resolution. The high charge density distribution on the surface generates an intense electric field that can induce ionization of gas atoms. We investigate the dynamic nature of the charge and the consequent electrostatic field redistribution following the departure of atoms initially constituting the surface in the form of an ion, a process known as field evaporation. We report on a new algorithm for image processing and tracking of individual atoms on the specimen surface enabling quantitative assessment of shifts in the imaged atomic positions. By combining experimental investigations with molecular dynamics simulations, which include the full electric charge, we confirm that change is directly associated with the rearrangement of the electrostatic field that modifies the imaging gas ionization zone. We derive important considerations for future developments of data reconstruction in 3D field ion microscopy, in particular for precise quantification of lattice strains and characterization of crystalline defects at the atomic scale. read less C. Yang and L. Qi, “Ab initio calculations of ideal strength and lattice instability in W-Ta and W-Re alloys,” Physical Review B. 2018. link Times cited: 15 Abstract: An important theoretical criterion to evaluate the ductility… read more Abstract: An important theoretical criterion to evaluate the ductility of metals with a body-centered cubic (bcc) lattice is the mechanical failure mode of their perfect crystals under tension along $\ensuremath{\langle}100\ensuremath{\rangle}$ directions. When the tensile stress reaches the ideal tensile strength, the pure W crystal fails by a cleavage fracture along the ${100}$ plane so that it is intrinsically brittle. To discover the strategy to improve its ductility, we performed density functional theory and density functional perturbation theory calculations to study the ideal tensile strength and the lattice instability under $\ensuremath{\langle}100\ensuremath{\rangle}$ tension for both W-Ta and W-Re alloys. Anisotropic linear elastic fracture mechanics (LEFM) theory and Rice's criterion were also applied to analyze the mechanical instability at the crack tip under $\ensuremath{\langle}100\ensuremath{\rangle}$ tension based on the competition between cleavage propagation and dislocation emission. The results show that the intrinsic ductility can be achieved in both W-Ta and W-Re, however, by different mechanisms. Even though W-Ta alloys with low Ta concentrations are still intrinsically brittle, the intrinsic ductility of W-Ta alloys with high Ta concentrations is promoted by elastic shear instability before the cleavage failure. The intrinsic ductility of W-Re alloys is produced by unstable transverse phonon waves before the cleavage failure, and the corresponding phonon mode is related to the generation of $\frac{1}{2}\ensuremath{\langle}111\ensuremath{\rangle}{\overline{2}11}$ dislocation in bcc crystals. The ideal tensile calculations, phonon analyses, and anisotropic LEFM examinations are mutually consistent in the evaluation of intrinsic ductility. These results bring us physical insights on the ductility-brittle mechanisms of W alloys under extreme stress conditions. read less S. Xu, Y. Su, D. Chen, and L. Li, “An atomistic study of the deformation behavior of tungsten nanowires,” Applied Physics A. 2017. link Times cited: 1 T. Frolov et al., “Grain boundary phases in bcc metals.,” Nanoscale. 2017. link Times cited: 52 Abstract: We report a computational discovery of novel grain boundary … read more Abstract: We report a computational discovery of novel grain boundary structures and multiple grain boundary phases in elemental body-centered cubic (bcc) metals represented by tungsten, tantalum and molybdenum. While grain boundary structures created by the γ-surface method as a union of two perfect half crystals have been studied extensively, it is known that the method has limitations and does not always predict the correct ground states. Herein, we use a newly developed computational tool, based on evolutionary algorithms, to perform a grand-canonical search of high-angle symmetric tilt and twist boundaries, and we find new ground states and multiple phases that cannot be described using the conventional structural unit model. We use molecular dynamics (MD) simulations to demonstrate that the new structures can coexist at finite temperature in a closed system, confirming that these are examples of different grain boundary phases. The new ground state is confirmed by first-principles calculations. read less G. Bonny, A. Bakaev, D. Terentyev, and Y. Mastrikov, “Interatomic potential to study plastic deformation in tungsten-rhenium alloys,” Journal of Applied Physics. 2017. link Times cited: 38 Abstract: In this work, an interatomic potential for the W-Re system i… read more Abstract: In this work, an interatomic potential for the W-Re system is fitted and benchmarked against experimental and density functional theory (DFT) data, of which part are generated in this work. Having in mind studies related to the plasticity of W-Re alloys under irradiation, emphasis is put on fitting point-defect properties, elastic constants, and dislocation properties. The developed potential can reproduce the mechanisms responsible for the experimentally observed softening, i.e., decreasing shear moduli, decreasing Peierls barrier, and asymmetric screw dislocation core structure with increasing Re content in W-Re solid solutions. In addition, the potential predicts elastic constants in reasonable agreement with DFT data for the phases forming non-coherent precipitates (σ- and χ-phases) in W-Re alloys. In addition, the mechanical stability of the different experimentally observed phases is verified in the temperature range of interest (700–1500 K). As a conclusion, the presented potential provides an exce... read less X.-X. Wang, L. Niu, and S. Wang, “Strong trapping and slow diffusion of helium in a tungsten grain boundary,” Journal of Nuclear Materials. 2017. link Times cited: 34 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 J. Hao, X. Shu, S. Jin, X. Zhang, Y. Zhang, and G. Lu, “A comparison of interatomic potentials for modeling tungsten nanocluster structures,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2017. link Times cited: 4 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 T. Swinburne et al., “Fast, vacancy-free climb of prismatic dislocation loops in bcc metals,” Scientific Reports. 2016. link Times cited: 52 M. Márquez-Mijares, B. Lepetit, and D. Lemoine, “Carbon adsorption on tungsten and electronic field emission,” Surface Science. 2016. link Times cited: 12 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 F. Zhou et al., “New interatomic potentials for studying the behavior of noble gas atoms in tungsten,” Journal of Nuclear Materials. 2015. link Times cited: 15 J. Fikar and R. Gröger, “Interactions of prismatic dislocation loops with free surfaces in thin foils of body-centered cubic iron,” Acta Materialia. 2015. link Times cited: 12 T. Swinburne, “Stochastic Dynamics of Crystal Defects.” 2015. link Times cited: 5 B. K. Vanleeuwen and V. Gopalan, “The antisymmetry of distortions,” Nature Communications. 2015. link Times cited: 7 S. Fitzgerald, “Crowdion–solute interactions: Analytical modelling and stochastic simulation,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2015. link Times cited: 6 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 more Abstract: 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 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 S. G. D. Vicente, S. Dudarev, and M. Rieth, “Overview of the Structural Materials Program for Fusion Reactors under EFDA,” Fusion Science and Technology. 2014. link Times cited: 7 Abstract: The Fusion Materials Topical Group (FMTG) coordinates, under… read more Abstract: The Fusion Materials Topical Group (FMTG) coordinates, under the European Fusion Development Agreement (EFDA), the EU effort on the development of structural and protection materials for the very demanding operating conditions of a future DEMO reactor. The reference documents for this program are the European Roadmap for Fusion and the Materials Assessment Group (MAG) report. The FMTG work or EFDA work is structured as follows: a) Integrated radiation effects modelling and experimental validation: focused on the development of a conceptual and quantitative framework for the interpretation of experimental tests on steels and iron-based alloys and tungsten and tungsten alloys and predicting the performance of these materials under DEMO-relevant operating conditions. b) High heat flux materials: focused on the development of materials for armour applications (W alloys), structural applications for low and high temperature cooling concepts (Cu-based alloys, W-based alloys), materials technologies (joining, fabrication), and testing of prototype of cooling structures. c) Nano-structured oxide dispersion strengthened (ODS) ferritic steel development: focused on the development of an ODS ferritic steel with high tensile and creep strength and sufficient ductility and fracture toughness up to about 750°C, as well as good radiation resistance. d) Materials database status and needs for DEMO conceptual design activities: focused on the assessment and analysis of fusion materials available data, identifying areas of uncertainties and conditions (relevant to the design) where data are either missing or unreliable. read less Q. Meng-fei, W. Ying-Min, Z. Hong-Yu, and S. Ji-Zhong, “Dynamic migration of <100> interstitial dislocation loops under pure W and W containing helium impurity (010) surfaces studied by molecular dynamics simulation,” Acta Physica Sinica. 2023. link Times cited: 0 Abstract: In the fusion irradiation environment, dislocation loop defe… read more Abstract: In the fusion irradiation environment, dislocation loop defects occur under the plasma-facing tungsten surfaces, which affect its mechanical properties and hydrogen/helium retention. This paper presents a study that dynamic behaviors of a loop with a radius of 1 nm under the W surface are simulated by using molecular dynamics simulation at the atomic level. It finds that the dislocation loop direction, bulk temperature, depth, and helium atoms have great influence on the motion of the dislocation. This study shows that the dislocation loop ( is the Burgers vector, is the surface normal direction) tends to move towards the surface and the dislocation loop tends to stay in the material. In the course of its migration, the habit plane of dislocation loop may change and the internal stress reduces gradually. The probability of a dislocation loops escaping from the surface is over 90% when the temperature is higher than 800 K and their initial depth is less than 5 nm. The dislocation loop can escape from the surface when the temperature is 800 K and the initial depth is less than 2 nm. It is found that dislocation loops decompose into dislocations at elevated temperatures. Helium atoms impedes the migration of dislocation loop and increases its retention time. The existence of dislocation loops results in the uneven distribution of helium atoms under the W surface, and will potentially affect the surface morphology of tungsten. read less M. E. Stupak, M. G. Urazaliev, and V. Popov, “Energies of point defects formation in tilt grain boundaries <110> in tungsten,” THE VIII INTERNATIONAL YOUNG RESEARCHERS’ CONFERENCE – PHYSICS, TECHNOLOGY, INNOVATIONS (PTI-2021). 2022. link Times cited: 0 I. Shepelev and E. Korznikova, “Comparison of 4-crowdion propagation dynamics in FCC and BCC lattices,” MATHEMATICS EDUCATION AND LEARNING. 2022. link Times cited: 0 A. Bayazitov, R. Murzaev, and Y. V. Bebikhov, “Effect of interatomic potentials on dynamics of supersonic 2-crowdions in tungsten,” MATHEMATICS EDUCATION AND LEARNING. 2022. link Times cited: 2 B. Fu, M. Qiu, J. Cui, J. Wang, and Q. Hou, “Diffusion, Trapping, and Dissociation Behaviours of Helium at the Σ5 Grain Boundary in Tungsten: A Molecular Dynamics Study,” Journal of Nuclear Materials. 2021. link Times cited: 9 P. Li, L. Wang, S.-liang Yan, M. Meng, Y. Zhou, and K. Xue, “The role of non-equilibrium grain boundary in micro-deformation and failure mechanisms of Bicrystal structural tungsten,” International Journal of Refractory Metals & Hard Materials. 2021. link Times cited: 4 M. Qiu, A. Yang, L. Zhai, B. Fu, and Q. Hou, “The calculation of the dissociation of hydrogen from helium clusters in tungsten,” Journal of Nuclear Materials. 2020. link Times cited: 4 P. Li, T. Wu, J. Shu, Y. Zhou, X. Wang, and K. Xue, “Phase transformation of pure tungsten subjected to multi-directional compression,” International Journal of Refractory Metals & Hard Materials. 2020. link Times cited: 2 L.-F. Wang, X. Shu, D. Lin, G. Lu, and H. Song, “Molecular dynamics studies of hydrogen diffusion in tungsten at elevated temperature: Concentration dependence and defect effects,” International Journal of Hydrogen Energy. 2020. link Times cited: 9 Y. G. Osetsky and D. Rodney, “Atomic-Level Dislocation Dynamics in Irradiated Metals,” Comprehensive Nuclear Materials. 2020. link Times cited: 8 T. Swinburne, “Atomistic Simulations in bcc Metals.” 2015. link Times cited: 0 T. Swinburne, “The Stochastic Force on Crystal Defects.” 2015. link Times cited: 1 M. Hodapp, “Machine learning is funny but physics makes the money: How machine-learning potentials can advance computer-aided materials design in metallurgy,” Computational Materials Science. 2024. link Times cited: 0 G. S. Dhaliwal, P. Nair, and C. V. Singh, “Machine learned interatomic potentials using random features,” npj Computational Materials. 2022. link Times cited: 10 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 more Abstract: 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 S. Makri, C. Ortner, and J. Kermode, “A preconditioning scheme for minimum energy path finding methods.,” The Journal of chemical physics. 2018. link Times cited: 11 Abstract: Popular methods for identifying transition paths between ene… read more Abstract: Popular methods for identifying transition paths between energy minima, such as the nudged elastic band and string methods, typically do not incorporate potential energy curvature information, leading to slow relaxation to the minimum energy path for typical potential energy surfaces encountered in molecular simulation. We propose a preconditioning scheme which, combined with a new adaptive time step selection algorithm, substantially reduces the computational cost of transition path finding algorithms. We demonstrate the improved performance of our approach in a range of examples including vacancy and dislocation migration modeled with both interatomic potentials and density functional theory. read less N. Castin et al., “Advanced atomistic models for radiation damage in Fe-based alloys: Contributions and future perspectives from artificial neural networks,” Computational Materials Science. 2018. link Times cited: 21 С. Волегов, Р. М. Герасимов, and Р. П. Давлятшин, “MODELS OF MOLECULAR DYNAMICS: A REVIEW OF EAM-POTENTIALS. PART 2. POTENTIALS FOR MULTI-COMPONENT SYSTEMS.” 2018. link Times cited: 1 Abstract: Получена: 18 мая 2018 г. Принята: 25 июня 2018 г. Опубликова… read more Abstract: Получена: 18 мая 2018 г. Принята: 25 июня 2018 г. Опубликована: 29 июня 2018 г. В статье представлена вторая часть обзора современных подходов и работ, посвященных построению потенциалов межатомного взаимодействия с использованием методологии погруженного атома (EAM-потенциалы). Эта часть обзора посвящена одной из наиболее остро стоящих проблем в молекулярной динамике – вопросам построения потенциалов, которые были бы пригодны для описания структуры и физико-механических свойств многокомпонентных (в первую очередь – бинарных и тернарных) материалов. Отмечены первые работы, в которых предлагались подходы к построению функций перекрестного взаимодействия для сплавов никеля и меди – как с использованием методологии EAM, так и несколько отличающийся по процедуре построения потенциал типа Финисса-Синклера. Рассматриваются работы, в которых производится сопоставление различных подходов к построению потенциалов, а также к процедуре идентификации их параметров на примере одних и тех же многокомпонентных систем (типа Al-Ni или Cu-Au). Кроме того, особый интерес представляют некоторые тернарные системы, например Fe–Ni–Cr, W–H– He или U–Mo–Xe, которые являются ключевыми для материалов атомной энергетики и которые в последние годы активно изучаются как возможные материалы для использования в термоядерных ректорах. Приведены примеры работ, в которых предлагаются и исследуются потенциалы для описания многокомпонентных систем, пригодных для использования в аэрокосмической промышленности и изготовленных прежде всего на основе никеля. Рассмотрены результаты исследований различных интерметаллических соединений, отмечены работы, в которых при помощи построенного EAM потенциала удалось количественно точно описать фазовые диаграммы соединений и вычислить характеристики фазовых переходов. read less R. Wang et al., “Classical and machine learning interatomic potentials for BCC vanadium,” Physical Review Materials. 2022. link Times cited: 3 Abstract: BCC transition metals (TMs) exhibit complex temperature and … read more Abstract: BCC transition metals (TMs) exhibit complex temperature and strain-rate dependent plastic deformation behaviour controlled by individual crystal lattice defects. Classical empirical and semi-empirical interatomic potentials have limited capability in modelling defect properties such as the screw dislocation core structures and Peierls barriers in the BCC structure. Machine learning (ML) potentials, trained on DFT-based datasets, have shown some successes in reproducing dislocation core properties. However, in group VB TMs, the most widely-used DFT functionals produce erroneous shear moduli C 44 which are undesirably transferred to machine-learning interatomic potentials, leaving current ML approaches unsuitable for this important class of metals and alloys. Here, we develop two interatomic potentials for BCC vanadium (V) based on (i) an extension of the partial electron density and screening parameter in the classical semi-empirical modiﬁed embedded-atom method (XMEAM-V) and (ii) a recent hybrid descriptor in the ML Deep Potential framework (DP-HYB-V). We describe distinct features in these two disparate approaches, including their dataset generation, training procedure, weakness and strength in modelling lattice and defect properties in BCC V. Both XMEAM-V and DP-HYB-V reproduce a broad range of defect properties (vacancy, self-interstitials, surface, dislocation) relevant to plastic deformation and fracture. In particular, XMEAM-V reproduces nearly all mechanical and thermodynamic properties at DFT accuracies and with C 44 near experimental value. XMEAM-V also naturally exhibits the anomalous slip at 77 K widely observed in group VB and VIB TMs and outperforms all existing, publically available interatomic potentials for V. The XMEAM thus provides a practical path to developing accurate and efﬁcient interatomic potentials for nonmagnetic BCC TMs and possibly multi-principal element TM alloys. read less J. Qi, C. Oberdorfer, W. Windl, and E. Marquis, “Ab initio simulation of field evaporation,” Physical Review Materials. 2022. link Times cited: 5 Abstract: A new simulation approach of field evaporation is presented.… read more Abstract: A new simulation approach of field evaporation is presented. The model combines classical electrostatics with molecular dynamics (MD) simulations. Unlike previous atomic-level simulation approaches, our method does not rely on an evaporation criterion based on thermal activation theory, instead, electric-field-induced forces on atoms are explicitly calculated and added to the interatomic forces. Atoms then simply move according to the laws of classical molecular dynamics and are"evaporated"when the external force overcomes interatomic bonding. This approach thus makes no ad-hoc assumptions concerning evaporation fields and criteria, which makes the simulation fully physics-based and"ab-initio"apart from the interatomic potential. As proof of principle, we perform simulations to determine material dependent critical voltages which allow assessing the evaporation fields and the corresponding steady-state tip shapes in different metals. We also extract critical evaporation fields in elemental metals and sublimation energies in a high entropy alloy to have a more direct comparison with tabulated values. In contrast to previous approaches, we show that our method is able to successfully reproduce the enhanced zone lines observed in experimental field desorption patterns. We also demonstrate the need for careful selection of the interatomic potential by a comparative study for the example of Cu-Ni alloys. read less G. Baldinozzi and V. Pontikis, “Phenomenological potentials for the refractory metals Cr, Mo and W,” Journal of Physics: Condensed Matter. 2022. link Times cited: 1 Abstract: Cohesion in the refractory metals Cr, Mo, and W is phenomeno… read more Abstract: Cohesion in the refractory metals Cr, Mo, and W is phenomenologically described in this work via a n-body energy functional with a set of physically motivated parameters that were optimized to reproduce selected experimental properties characteristic of perfect and defective crystals. The functional contains four terms accounting for the hard-core repulsion, the Thomas–Fermi kinetic energy repulsion and for contributions to the binding energy of s and d valence electrons. Lattice dynamics, molecular statics, and molecular dynamics calculations show that this model describes satisfactorily thermodynamic properties of the studied metals whereas, unlike other empirical approaches from the literature, predictions of phonon dispersion relations and of surface and point defect energetics reveal in fair good agreement with experiments. These results suggest that the present model is well adapted to large-scale simulations and whenever total energy calculations of thermodynamic properties are unfeasible. read less 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 more Abstract: 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 A. Goryaeva et al., “Efficient and transferable machine learning potentials for the simulation of crystal defects in bcc Fe and W,” Physical Review Materials. 2021. link Times cited: 20 Abstract: .… read more Abstract: . read less S. Xie, M. Rupp, and R. Hennig, “Ultra-fast interpretable machine-learning potentials,” npj Computational Materials. 2021. link Times cited: 9 Q. Yang and P. Olsson, “Full energy range primary radiation damage model,” Physical Review Materials. 2021. link Times cited: 9 Abstract: A full energy range primary radiation damage model is presen… read more Abstract: A full energy range primary radiation damage model is presented here. It is based on the athermal recombination corrected displacements per atom (arc-dpa) model but includes a proper treatment of the near threshold conditions for metallic materials. Both ab initio (AIMD) and classical molecular dynamics (MD) simulations are used here for various metals with body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal close-packed (hcp) structures to validate the model. For bcc and hcp metals, the simulation results fit very well with the model. For fcc metals, although there are slight deviations between the model and direct simulation results, it is still a clear improvement on the arc-dpa model. The deviations are due to qualitative differences in the threshold energy surfaces of fcc metals with respect to bcc and hcp metals according to our classical MD simulations. We introduce the minimum threshold displacement energy (TDE) as a term in our damage model. We calculated minimum TDEs for various metal materials using AIMD. In general, the calculated minimum TDEs are in very good agreement with experimental results. Moreover, we noticed a discrepancy in the literature for fcc Ni and estimated the average TDE of Ni using both classical MD and AIMD. It was found that the average TDE of Ni should be \ensuremath{\sim}70 eV based on simulation and experimental data, not the commonly used literature value of 40 eV. The most significant implications of introducing this full energy range damage model will be for estimating the effect of weak particle-matter interactions, such as for \ensuremath{\gamma}- and electron-radiation-induced damage. read less 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 more Abstract: 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 E. Clouet, B. Bienvenu, L. Dezerald, and D. Rodney, “Screw dislocations in BCC transition metals: from ab initio modeling to yield criterion,” Comptes Rendus. Physique. 2021. link Times cited: 19 Abstract: We show here how density functional theory calculations can … read more Abstract: We show here how density functional theory calculations can be used to predict the temperatureand orientation-dependence of the yield stress of body-centered cubic (BCC) metals in the thermallyactivated regime where plasticity is governed by the glide of screw dislocations with a 1/2 Burgers vector. Our numerical model incorporates non-Schmid effects, both the twinning/antitwinning asymmetry and non-glide effects, characterized through ab initio calculations on straight dislocations. The model uses the stress-dependence of the kink-pair nucleation enthalpy predicted by a line tension model also fully parameterized on ab initio calculations. The methodology is illustrated here on BCC tungsten but is applicable to all BCC metals. Comparison with experimental data allows to highlight both the successes and remaining limitations of our modeling approach. read less N. Kvashin, N. Anento, D. Terentyev, A. Bakaev, and A. Serra, “Interaction of a dislocation pileup with 332 tilt grain boundary in bcc metals studied by MD simulations,” Physical Review Materials. 2021. link Times cited: 7 Abstract: The sustainability and capacity of macroscopic deformation b… read more Abstract: The sustainability and capacity of macroscopic deformation by polycrystalline metals and metallic alloys is controlled by the propagation of dislocation-mediated slip through grains. In this paper, the interaction of a pileup of $1/2\ensuremath{\langle}111\ensuremath{\rangle}$ dislocations with the ${332}$ tilt grain boundary (GB) is studied as a function of temperature in three bcc metals: iron (Fe), chromium (Cr), and tungsten (W). The interaction results in the transformation of the crystal dislocation into GB dislocations. The ${332}$ tilt GB absorbs the crystal dislocations of the pileup, neither the transmission nor reflection of dislocations was observed. The reaction product at the GB is determined by the crystallography of the GB and the features of the crystal dislocations involved, specifically, the orientation of the Burgers vector and the glide plane of the dislocation. In general, the decomposition results in the formation of a sessile GB dislocation with a riser that facets the GB and several elementary disconnections that glide away. In some cases, the riser increases its length with the number of dislocations absorbed and a new asymmetrical grain boundary of ${112}/{110}$ type is created. For a given external shear stress, the number of dislocations absorbed depends on the orientation of the Burgers vector, glide plane of the pileup, and material. read less A. Goryaeva, C. Lapointe, C. Dai, J. Dérès, J. Maillet, and M. Marinica, “Reinforcing materials modelling by encoding the structures of defects in crystalline solids into distortion scores,” Nature Communications. 2020. link Times cited: 27 K. Kowalczyk-Gajewska and M. Ma’zdziarz, “Elastic properties of nanocrystalline materials of hexagonal symmetry: The core-shell model and atomistic estimates,” International Journal of Engineering Science. 2020. link Times cited: 5 M. E. Stupak, M. G. Urazaliev, and V. Popov, “Structure and Energy of 〈110〉 Symmetric Tilt Boundaries in Polycrystalline Tungsten,” Physics of Metals and Metallography. 2020. link Times cited: 3 M. Boleininger, M. Gallauer, S. Dudarev, T. Swinburne, D. Mason, and D. Perez, “Statistical mechanics of kinks on a gliding screw dislocation,” arXiv: Materials Science. 2020. link Times cited: 2 Abstract: The ability of a body-centered cubic metal to deform plastic… read more Abstract: The ability of a body-centered cubic metal to deform plastically is limited by the thermally activated glide motion of screw dislocations, which are line defects with a mobility exhibiting complex dependence on temperature, stress, and dislocation segment length. We derive an analytical expression for the velocity of dislocation glide, based on a statistical mechanics argument, and identify an apparent phase transition marked by a critical temperature above which the activation energy for glide effectively halves, changing from the formation energy of a double kink to that of a single kink. The analysis is in quantitative agreement with direct kinetic Monte Carlo simulations. read less B. Gurrutxaga-Lerma, J. Verschueren, A. Sutton, and D. Dini, “The mechanics and physics of high-speed dislocations: a critical review,” International Materials Reviews. 2020. link Times cited: 34 Abstract: ABSTRACT High speed dislocations have long been identified a… read more Abstract: ABSTRACT High speed dislocations have long been identified as the dominant feature governing the plastic response of crystalline materials subjected to high strain rates, controlling deformation and failure in industrial processes such as machining, laser shock peening, punching, drilling, crashworthiness, foreign object damage, etc. Despite decades of study, the role high speed dislocations have on the materials response remains elusive. This article reviews both experimental and theoretical efforts made to address this issue in a systematic way. The lack of experimental evidence and direct observation of high speed dislocations means that most work on the matter is rooted on theory and simulations. This article offers a critical review of the competing theoretical accounts of high speed mechanisms, their underlying hypothesis, insights, and shortcomings, with particular focus on elastic continuum and atomistic levels. The article closes with an overview of the current state of the art and suggestions for key developments in future research. read less P. Grigorev, T. Swinburne, and J. Kermode, “Hybrid quantum/classical study of hydrogen-decorated screw dislocations in tungsten: Ultrafast pipe diffusion, core reconstruction, and effects on glide mechanism,” Physical Review Materials. 2020. link Times cited: 10 Abstract: The interaction of hydrogen (H) with dislocations in tungste… read more Abstract: The interaction of hydrogen (H) with dislocations in tungsten (W) must be understood in order to model the mechanical response of future plasma-facing materials for fusion applications. Here, hybrid quantum mechanics/molecular mechanics (QM/MM) simulations are employed to study the ⟨111⟩ screw dislocation glide in W in the presence of H, using the virtual work principle to obtain energy barriers for dislocation glide, H segregation, and pipe diffusion. We provide a convincing validation of the QM/MM approach against full DFT energy-based methods. This is possible because the compact core and relatively weak elastic fields of ⟨111⟩ screw dislocations allow them to be contained in periodic DFT supercells. We also show that H segregation stabilizes the split-core structure while leaving the Peierls barrier almost unchanged. Furthermore, we find an energy barrier of less than 0.05 eV for pipe diffusion of H along dislocation cores. Our quantum-accurate calculations provide important reference data for the construction of larger-scale material models. read less N. Mathew, D. Perez, and E. Martínez, “Atomistic simulations of helium, hydrogen, and self-interstitial diffusion inside dislocation cores in tungsten,” Nuclear Fusion. 2020. link Times cited: 7 Abstract: Tritium retention and microstructural modifications due to h… read more Abstract: Tritium retention and microstructural modifications due to helium accumulation are two of the main concerns regarding plasma-facing materials in fusion applications. Crystal defects in tungsten (W), such as grain boundaries and dislocations, can serve as traps or channels for diffusion of hydrogen (H) and helium (He), and, as such, can affect the transport of these species. In this work, we study the diffusion of hydrogen, helium and self-interstitial atoms (SIA) inside screw and edge dislocations in W using molecular dynamics simulations. Stable sites for interstitials in dislocations are identified using a free-volume analysis and energy barriers for diffusion are predicted using a combination of the nudged elastic band (NEB) method and finite temperature molecular dynamics simulations. Overall, the simulations predict higher energetic barriers for He and H diffusion in both screw and edge dislocations compared to the bulk. However, the diffusion mechanism in both dislocations are shown to differ: simulations predict that interstitials are constrained to move in short channels inside the edge dislocation core so that long-range diffusion along the dislocation line happens only with the motion of the dislocation. In contrast, 1D diffusion of the interstitial along the dislocation core, independent of dislocation motion, is observed for screw dislocations. read less S. Yin, J. Ding, M. Asta, and R. Ritchie, “Ab initio modeling of the energy landscape for screw dislocations in body-centered cubic high-entropy alloys,” npj Computational Materials. 2019. link Times cited: 55 A. Markidonov, M. Starostenkov, P. Zakharov, D. Lubyanoi, and V. N. Lipunov, “Emission of Dislocation Loops from Nanovoids in an FCC Crystal Subjected to Shear Deformation under Post-Cascade Shock Waves,” Journal of Experimental and Theoretical Physics. 2019. link Times cited: 3 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 more Abstract: 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 S. Pozdnyakov, A. Oganov, E. Mazhnik, A. Mazitov, and I. Kruglov, “Fast general two- and three-body interatomic potential,” Physical Review B. 2019. link Times cited: 6 Abstract: We introduce a new class of machine learning interatomic pot… read more Abstract: We introduce a new class of machine learning interatomic potentials - fast General Two- and Three-body Potential (GTTP) which are as fast as conventional empirical potentials and require computational time that remains constant with increasing fitting flexibility. GTTP does not contain any assumptions about functional form of two- and three-body interactions. These interactions can be modeled arbitrarily accurately potentially by thousands of parameters not affecting resulting computational cost. Time complexity is O(1) per every considered pair or triple of atoms. The fitting procedure is reduced to simple linear regression on ab initio calculated energies and forces and leads to effective two- and three-body potential which reproduces quantum many-body interactions as accurately as possible. Our potential can be made continuously differentiable any number of times at the expense of increased computational time. We made a number of performance tests on one-, two- and three-component systems. Flexibility of the introduced approach makes the potential transferable in terms of size and type of atomic systems. We show, that trained on randomly generated structures with just 8 atoms in the unit cell, it significantly outperforms common empirical interatomic potentials in the study of large systems, such as grain boundaries in polycrystalline materials. read less 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 more Abstract: 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 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 more Abstract: 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 F. Hofmann et al., “Nanoscale imaging of the full strain tensor of specific dislocations extracted from a bulk sample,” Physical Review Materials. 2019. link Times cited: 27 Abstract: Lattice defects play a key role in determining the propertie… read more Abstract: Lattice defects play a key role in determining the properties of crystalline materials. Probing the 3D lattice strains that govern their interactions remains a challenge. Bragg Coherent Diffraction Imaging (BCDI) allows strain to be measured with nano-scale 3D resolution. However, it is currently limited to materials that form micro-crystals. Here we introduce a new technique that allows the manufacture of BCDI samples from bulk materials. Using tungsten as an example, we show that focussed ion beam (FIB) machining can be used to extract, from macroscopic crystals, micron-sized BCDI samples containing specific pre-selected defects. To interpret the experimental data, we develop a new displacement-gradient-based analysis for multi-reflection BCDI. This allows accurate recovery of the full lattice strain tensor from samples containing multiple dislocations. These new capabilities open the door to BCDI as a microscopy tool for studying complex real-world materials. read less 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 more Abstract: 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 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 more Abstract: 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 P. Grigorev et al., “Molecular dynamics simulation of hydrogen and helium trapping in tungsten,” Journal of Nuclear Materials. 2018. link Times cited: 18 M. Boleininger, T. Swinburne, and S. Dudarev, “Atomistic-to-continuum description of edge dislocation core: Unification of the Peierls-Nabarro model with linear elasticity,” Physical Review Materials. 2018. link Times cited: 16 Abstract: Conventional linear elasticity theory predicts the strain fi… read more Abstract: Conventional linear elasticity theory predicts the strain fields of a dislocation core to diverge, whereas it is known from atomistic simulations that core strains should remain finite. We present an analytical solution to a generalized, variational Peierls-Nabarro model of edge dislocation displacement fields that features a finite core width and correct isotropic elastic behavior at large distances away from the core. We derive an analytical expression for the dislocation core radius, representing the convergence radius of the linear elasticity far-field expansion. The strain fields are in qualitative agreement with atomistic simulations of 12[111](10¯1) edge dislocations in bcc tungsten and iron. The treatment is based on the multistring Frenkel-Kontorova model that we reformulate as a generalized Peierls-Nabarro model using the principle of least action. read less T. Swinburne and S. Dudarev, “Kink-limited Orowan strengthening explains the brittle to ductile transition of irradiated and unirradiated bcc metals,” Physical Review Materials. 2018. link Times cited: 20 Abstract: The line tension model of obstacle hardening is modified to … read more Abstract: The line tension model of obstacle hardening is modified to account for the thermally activated, kink-limited glide of 1/2111 screw dislocations, allowing application to the plastic flow of bcc metals. Using atomistically informed dislocation mobility laws, Frenkel-Kontorova simulations, and a simplified dislocation-obstacle model, we identify a size effect for intermediate obstacle densities, where the activation energy for screw dislocation motion halves once the obstacle density falls below a critical value. Our model shows striking agreement with fracture experiments across a wide range of unirradiated and irradiated bcc metals. In particular, we demonstrate that the presence of defects in the crystal lattice can at most double the brittle to ductile transition temperature. read less 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 more Abstract: 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 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 more Abstract: 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 A. Bakaev, P. Grigorev, D. Terentyev, A. Bakaeva, E. Zhurkin, and Y. Mastrikov, “Trapping of hydrogen and helium at dislocations in tungsten: an ab initio study,” Nuclear Fusion. 2017. link Times cited: 36 Abstract: The interaction of H or He atoms with a core of edge and scr… read more Abstract: The interaction of H or He atoms with a core of edge and screw dislocations (SDs), with Burgers vector a0/2〈111〉, is studied by means of ab initio calculations. The results show that the edge dislocations are stronger traps for H and He compared to the SDs, while the H/He affinity to both types of dislocation is significantly weaker than to a single vacancy. The lowest energy atomic configurations are rationalized on the basis of the charge density distribution and elasticity theory considerations. The results obtained contribute to the rationalization of the thermal desorption spectroscopy analysis by attributing certain peaks of the release of plasma components to the detrapping from dislocations. Complementary molecular statics (MS) calculations are performed to validate the accuracy of the recently developed W–H–He embedded atom method (EAM) and bond-order potentials. It is revealed that the EAM potential can reproduce correctly the magnitude of the interaction of H with both dislocations as compared to the ab initio results. All the potentials underestimate significantly the He-dislocation interaction and cannot describe correctly the lowest energy positions for H and He around the dislocation core. The reason for the discrepancy between ab initio and the MS results is rationalized by the analysis of the fully relaxed atomic configurations. read less L.-F. Wang, X. Shu, G. Lu, and F. Gao, “Embedded-atom method potential for modeling hydrogen and hydrogen-defect interaction in tungsten,” Journal of Physics: Condensed Matter. 2017. link Times cited: 20 Abstract: An embedded-atom method potential has been developed for mod… read more Abstract: An embedded-atom method potential has been developed for modeling hydrogen in body-centered-cubic (bcc) tungsten by fitting to an extensive database of density functional theory (DFT) calculations. Comprehensive evaluations of the new potential are conducted by comparing various hydrogen properties with DFT calculations and available experimental data, as well as all the other tungsten–hydrogen potentials. The new potential accurately reproduces the point defect properties of hydrogen, the interaction among hydrogen atoms, the interplay between hydrogen and a monovacancy, and the thermal diffusion of hydrogen in tungsten. The successful validation of the new potential confirms its good reliability and transferability, which enables large-scale atomistic simulations of tungsten–hydrogen system. The new potential is afterward employed to investigate the interplay between hydrogen and other defects, including [1 1 1] self-interstitial atoms (SIAs) and vacancy clusters in tungsten. It is found that both the [1 1 1] SIAs and the vacancy clusters exhibit considerable attraction for hydrogen. Hydrogen solution and diffusion in strained tungsten are also studied using the present potential, which demonstrates that tensile (compressive) stress facilitates (impedes) hydrogen solution, and isotropic tensile (compressive) stress impedes (facilitates) hydrogen diffusion while anisotropic tensile (compressive) stress facilitates (impedes) hydrogen diffusion. read less 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 L. Vlček, W. Sun, and P. Kent, “Combining configurational energies and forces for molecular force field optimization.,” The Journal of chemical physics. 2017. link Times cited: 11 Abstract: While quantum chemical simulations have been increasingly us… read more Abstract: While quantum chemical simulations have been increasingly used as an invaluable source of information for atomistic model development, the high computational expenses typically associated with these techniques often limit thorough sampling of the systems of interest. It is therefore of great practical importance to use all available information as efficiently as possible, and in a way that allows for consistent addition of constraints that may be provided by macroscopic experiments. Here we propose a simple approach that combines information from configurational energies and forces generated in a molecular dynamics simulation to increase the effective number of samples. Subsequently, this information is used to optimize a molecular force field by minimizing the statistical distance similarity metric. We illustrate the methodology on an example of a trajectory of configurations generated in equilibrium molecular dynamics simulations of argon and water and compare the results with those based on the force matching method. read less 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 S. Saroukhani, “ATOMISTIC MODELING OF DISLOCATION MOTION AT EXPERIMENTAL TIME-SCALES.” 2017. link Times cited: 0 M. Backman, N. Juslin, G. Huang, and B. Wirth, “A W Ne interatomic potential for simulation of neon implantation in tungsten,” Journal of Nuclear Materials. 2016. link Times cited: 3 G. Po et al., “A phenomenological dislocation mobility law for bcc metals,” Acta Materialia. 2016. link Times cited: 162 P. Grigorev, D. Terentyev, G. Bonny, E. Zhurkin, G. Oost, and J. Noterdaeme, “Mobility of hydrogen-helium clusters in tungsten studied by molecular dynamics,” Journal of Nuclear Materials. 2016. link Times cited: 19 P. Grigorev, D. Terentyev, A. Bakaev, and E. E. Zhurkin, “Classical molecular dynamics simulation of the interaction of hydrogen with defects in tungsten,” Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques. 2016. link Times cited: 4 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 more Abstract: 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 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 more Abstract: 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 P. Grigorev, D. Terentyev, G. Bonny, E. Zhurkin, G. Oost, and J. Noterdaeme, “Interaction of hydrogen with dislocations in tungsten: An atomistic study,” Journal of Nuclear Materials. 2015. link Times cited: 32 J. Crocombette, P. Notargiacomo, and M. Marinica, “Effect of the variation of the electronic density of states of zirconium and tungsten on their respective thermal conductivity evolution with temperature,” Journal of Physics: Condensed Matter. 2015. link Times cited: 11 Abstract: The thermal conductivity of zirconium and tungsten above 500… read more Abstract: The thermal conductivity of zirconium and tungsten above 500 K is calculated with atomistic simulations using a combination of empirical potentials molecular dynamics and density functional theory calculations. The thermal conductivity is calculated in the framework of Kubo–Greenwood theory. The obtained values are in quantitative agreement with experiments. The fact that the conductivity of Zr increases with temperature while that of tungsten is essentially constant is reproduced by the calculations. The evolution with temperature of the electronic density of states of these two pseudo-gap metals proves to explain the observed variations of the conductivity. read less L. Dezerald, L. Proville, L. Ventelon, F. Willaime, and D. Rodney, “First-principles prediction of kink-pair activation enthalpy on screw dislocations in bcc transition metals: V, Nb, Ta, Mo, W, and Fe,” Physical Review B. 2015. link Times cited: 74 Abstract: extension. Interestingly, we find that the atomistic line te… read more Abstract: extension. Interestingly, we find that the atomistic line tension is more than twice the usual elastic estimates. The calculations also show interesting group tendencies with the line tension and kink-pair width larger in group V than in group VI elements. Finally, the present kink-pair activation energies are shown to compare qualitatively with experimental data and potential origins of quantitative discrepancies are discussed. read less 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 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 more Abstract: 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 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 more Abstract: 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
Funding	Not available

Short KIM ID The unique KIM identifier code.	MO_046576227003_000
Extended KIM ID The long form of the KIM ID including a human readable prefix (100 characters max), two underscores, and the Short KIM ID. Extended KIM IDs can only contain alpha-numeric characters (letters and digits) and underscores and must begin with a letter.	EAM_Dynamo_MarinicaVentelonGilbert_2013EAM4__MO_046576227003_000
DOI	10.25950/ce93b9c6 https://doi.org/10.25950/ce93b9c6 https://commons.datacite.org/doi.org/10.25950/ce93b9c6
KIM Item Type Specifies whether this is a Portable Model (software implementation of an interatomic model); Portable Model with parameter file (parameter file to be read in by a Model Driver); Model Driver (software implementation of an interatomic model that reads in parameters).	Portable Model using Model Driver EAM_Dynamo__MD_120291908751_005
Driver	EAM_Dynamo__MD_120291908751_005
KIM API Version	2.0
Potential Type	eam
Programming Language(s) The programming languages used in the code and the percentage of the code written in each one. "N/A" means "not applicable" and refers to model parameterizations which only include parameter tables and have no programming language.	N/A

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Grade	Name	Category	Brief Description	Full Results	Aux File(s)
P All elements claimed by model are supported in at least one of the tested configurations.	vc-species-supported-as-stated	mandatory	The model supports all species it claims to support; see full description.	Results	Files
P Periodic boundary conditions were correctly supported for all configurations that the model was able to compute.	vc-periodicity-support	mandatory	Periodic boundary conditions are handled correctly; see full description.	Results	Files
P Model energy has permutation symmetry for all configurations the model was able to compute.	vc-permutation-symmetry	mandatory	Total energy and forces are unchanged when swapping atoms of the same species; see full description.	Results	Files
B The letter grade B was assigned because the normalized error in the computation was 7.18892e-08 compared with a machine precision of 2.22045e-16. The letter grade was based on 'score=log10(error/eps)', with ranges A=[0, 7.5], B=(7.5, 10.0], C=(10.0, 12.5], D=(12.5, 15.0), F>15.0. 'A' is the best grade, and 'F' indicates failure.	vc-forces-numerical-derivative	consistency	Forces computed by the model agree with numerical derivatives of the energy; see full description.	Results	Files
P The model is C^1 continuous. This means that the model has continuous energy and continuous first derivative.	vc-dimer-continuity-c1	informational	The energy versus separation relation of a pair of atoms is C1 continuous (i.e. the function and its first derivative are continuous); see full description.	Results	Files
P Model energy and forces are invariant with respect to rigid-body motion (translation and rotation) for all configurations the model was able to compute.	vc-objectivity	informational	Total energy is unchanged and forces transform correctly under rigid-body translation and rotation; see full description.	Results	Files
P Model energy has inversion symmetry for all configurations the model was able to compute.	vc-inversion-symmetry	informational	Total energy is unchanged and forces change sign when inverting a configuration through the origin; see full description.	Results	Files
P No memory leak detected.	vc-memory-leak	informational	The model code does not have memory leaks (i.e. it releases all allocated memory at the end); see full description.	Results	Files
P All threads give identical results for tested case. Model appears to be thread-safe.	vc-thread-safe	mandatory	The model returns the same energy and forces when computed in serial and when using parallel threads for a set of configurations. Note that this is not a guarantee of thread safety; see full description.	Results	Files
P Unit conversion successful	vc-unit-conversion	mandatory	The model is able to correctly convert its energy and/or forces to different unit sets; see full description.	Results	Files

This bar chart plot shows the mono-atomic body-centered cubic (bcc) lattice constant predicted by the current model (shown in the unique color) compared with the predictions for all other models in the OpenKIM Repository that support the species. The vertical bars show the average and standard deviation (one sigma) bounds for all model predictions. Graphs are generated for each species supported by the model.

Species: W

Cohesive Energy Graph

This graph shows the cohesive energy versus volume-per-atom for the current mode for four mono-atomic cubic phases (body-centered cubic (bcc), face-centered cubic (fcc), simple cubic (sc), and diamond). The curve with the lowest minimum is the ground state of the crystal if stable. (The crystal structure is enforced in these calculations, so the phase may not be stable.) Graphs are generated for each species supported by the model.

Species: W

Diamond Lattice Constant

This bar chart plot shows the mono-atomic face-centered diamond lattice constant predicted by the current model (shown in the unique color) compared with the predictions for all other models in the OpenKIM Repository that support the species. The vertical bars show the average and standard deviation (one sigma) bounds for all model predictions. Graphs are generated for each species supported by the model.

Species: W

Dislocation Core Energies

This graph shows the dislocation core energy of a cubic crystal at zero temperature and pressure for a specific set of dislocation core cutoff radii. After obtaining the total energy of the system from conjugate gradient minimizations, non-singular, isotropic and anisotropic elasticity are applied to obtain the dislocation core energy for each of these supercells with different dipole distances. Graphs are generated for each species supported by the model.

Species: W

FCC Elastic Constants

This bar chart plot shows the mono-atomic face-centered cubic (fcc) elastic constants predicted by the current model (shown in blue) compared with the predictions for all other models in the OpenKIM Repository that support the species. The vertical bars show the average and standard deviation (one sigma) bounds for all model predictions. Graphs are generated for each species supported by the model.

Species: W

FCC Lattice Constant

This bar chart plot shows the mono-atomic face-centered cubic (fcc) lattice constant predicted by the current model (shown in red) compared with the predictions for all other models in the OpenKIM Repository that support the species. The vertical bars show the average and standard deviation (one sigma) bounds for all model predictions. Graphs are generated for each species supported by the model.

Species: W

FCC Stacking Fault Energies

This bar chart plot shows the intrinsic and extrinsic stacking fault energies as well as the unstable stacking and unstable twinning energies for face-centered cubic (fcc) predicted by the current model (shown in blue) compared with the predictions for all other models in the OpenKIM Repository that support the species. The vertical bars show the average and standard deviation (one sigma) bounds for all model predictions. Graphs are generated for each species supported by the model.

(No matching species)

FCC Surface Energies

This bar chart plot shows the mono-atomic face-centered cubic (fcc) relaxed surface energies predicted by the current model (shown in blue) compared with the predictions for all other models in the OpenKIM Repository that support the species. The vertical bars show the average and standard deviation (one sigma) bounds for all model predictions. Graphs are generated for each species supported by the model.

(No matching species)

SC Lattice Constant

This bar chart plot shows the mono-atomic simple cubic (sc) lattice constant predicted by the current model (shown in the unique color) compared with the predictions for all other models in the OpenKIM Repository that support the species. The vertical bars show the average and standard deviation (one sigma) bounds for all model predictions. Graphs are generated for each species supported by the model.

Species: W

Cubic Crystal Basic Properties Table

Species: W

Tests

CohesiveEnergyVsLatticeConstant__TD_554653289799_003

Cohesive energy versus lattice constant curve for monoatomic cubic lattices v003

Creators:
Contributor: karls
Publication Year: 2019
DOI: https://doi.org/10.25950/64cb38c5

This Test Driver uses LAMMPS to compute the cohesive energy of a given monoatomic cubic lattice (fcc, bcc, sc, or diamond) at a variety of lattice spacings. The lattice spacings range from a_min (=a_min_frac*a_0) to a_max (=a_max_frac*a_0) where a_0, a_min_frac, and a_max_frac are read from stdin (a_0 is typically approximately equal to the equilibrium lattice constant). The precise scaling and number of lattice spacings sampled between a_min and a_0 (a_0 and a_max) is specified by two additional parameters passed from stdin: N_lower and samplespacing_lower (N_upper and samplespacing_upper). Please see README.txt for further details.

Test	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Cohesive energy versus lattice constant curve for bcc W v004	view	53430
Cohesive energy versus lattice constant curve for diamond W v004	view	60939
Cohesive energy versus lattice constant curve for fcc W v004	view	51411
Cohesive energy versus lattice constant curve for sc W v004	view	54146

DislocationCoreEnergyCubic__TD_452950666597_002

Dislocation core energy for cubic crystals at a set of dislocation core cutoff radii v002

Creators:
Contributor: qyc081025
Publication Year: 2023
DOI: https://doi.org/10.25950/ebecf626

This Test Driver computes the dislocation core energy of a cubic crystal at zero temperature and pressure for a specific set of dislocation core cutoff radii. First, it generates several periodic atomistic supercells containing a dislocation dipole. After obtaining the total energy of the system from conjugate gradient minimizations, non-singular, isotropic and anisotropic elasticity are applied to obtain the dislocation core energy for each of these supercells with different dipole distances. The supercell is increased in size until the disolcation core energy converges. Finally, after checking the independence of the results from the simulation cell geometry, the dislocation core energies are determined for each dislocation core radius.

Test	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [1, 1, 0] v000	view	8966167
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [1, 1, 1] v000	view	6550356
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [1, 1, 2] v000	view	26550578
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [1, 1, 3] v000	view	25310802
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [1, 1, 4] v000	view	22534499
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [1, 1, 5] v000	view	42108271
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [1, 1, 6] v000	view	45399701
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [1, 1, 7] v000	view	147287668
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [1, 1, -1] v000	view	68602232
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [2, 2, 3] v000	view	19952929
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [2, 2, 5] v000	view	91958409
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [2, 2, -1] v000	view	191547216
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [2, 2, -3] v000	view	235471982

ElasticConstantsCubic__TD_011862047401_006

Elastic constants for cubic crystals at zero temperature and pressure v006

Creators: Junhao Li and Ellad Tadmor
Contributor: tadmor
Publication Year: 2019
DOI: https://doi.org/10.25950/5853fb8f

Computes the cubic elastic constants for some common crystal types (fcc, bcc, sc, diamond) by calculating the hessian of the energy density with respect to strain. An estimate of the error associated with the numerical differentiation performed is reported.

Test	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Elastic constants for bcc W at zero temperature v006	view	2015
Elastic constants for diamond W at zero temperature v001	view	4159
Elastic constants for fcc W at zero temperature v006	view	1919
Elastic constants for sc W at zero temperature v006	view	2175

ElasticConstantsHexagonal__TD_612503193866_004

Elastic constants for hexagonal crystals at zero temperature v004

Creators: Junhao Li
Contributor: jl2922
Publication Year: 2019
DOI: https://doi.org/10.25950/d794c746

Computes the elastic constants for hcp crystals by calculating the hessian of the energy density with respect to strain. An estimate of the error associated with the numerical differentiation performed is reported.

Test	Test Results	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Elastic constants for hcp W at zero temperature v004		view	1783

EquilibriumCrystalStructure__TD_457028483760_003

Equilibrium structure and energy for a crystal structure at zero temperature and pressure v003

Creators:
Contributor: ilia
Publication Year: 2025
DOI: https://doi.org/10.25950/866c7cfa

Computes the equilibrium crystal structure and energy for an arbitrary crystal at zero temperature and applied stress by performing symmetry-constrained relaxation. The crystal structure is specified using the AFLOW prototype designation. Multiple sets of free parameters corresponding to the crystal prototype may be specified as initial guesses for structure optimization. No guarantee is made regarding the stability of computed equilibria, nor that any are the ground state.

Test	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Equilibrium crystal structure and energy for W in AFLOW crystal prototype A_cF4_225_a v003	view	183921
Equilibrium crystal structure and energy for W in AFLOW crystal prototype A_cI2_229_a v003	view	149044
Equilibrium crystal structure and energy for W in AFLOW crystal prototype A_cP8_223_ac v003	view	171890

LatticeConstantCubicEnergy__TD_475411767977_007

Equilibrium lattice constant and cohesive energy of a cubic lattice at zero temperature and pressure v007

Creators: Daniel S. Karls and Junhao Li
Contributor: karls
Publication Year: 2019
DOI: https://doi.org/10.25950/2765e3bf

Equilibrium lattice constant and cohesive energy of a cubic lattice at zero temperature and pressure.

Test	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Equilibrium zero-temperature lattice constant for bcc W v007	view	4319
Equilibrium zero-temperature lattice constant for diamond W v007	view	6750
Equilibrium zero-temperature lattice constant for fcc W v007	view	4382
Equilibrium zero-temperature lattice constant for sc W v007	view	4382

LatticeConstantHexagonalEnergy__TD_942334626465_005

Equilibrium lattice constants for hexagonal bulk structures at zero temperature and pressure v005

Creators: Daniel S. Karls and Junhao Li
Contributor: karls
Publication Year: 2019
DOI: https://doi.org/10.25950/c339ca32

Calculates lattice constant of hexagonal bulk structures at zero temperature and pressure by using simplex minimization to minimize the potential energy.

Test	Test Results	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Equilibrium lattice constants for hcp W v005		view	29034

LinearThermalExpansionCoeffCubic__TD_522633393614_002

Linear thermal expansion coefficient of cubic crystal structures v002

Creators:
Contributor: mjwen
Publication Year: 2024
DOI: https://doi.org/10.25950/9d9822ec

This Test Driver uses LAMMPS to compute the linear thermal expansion coefficient at a finite temperature under a given pressure for a cubic lattice (fcc, bcc, sc, diamond) of a single given species.

Test	Test Results	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Linear thermal expansion coefficient of bcc W at 293.15 K under a pressure of 0 MPa v002		view	677235

SurfaceEnergyCubicCrystalBrokenBondFit__TD_955413365818_004

High-symmetry surface energies in cubic lattices and broken bond model v004

Creators: Matt Bierbaum
Contributor: mattbierbaum
Publication Year: 2019
DOI: https://doi.org/10.25950/6c43a4e6

Calculates the surface energy of several high symmetry surfaces and produces a broken-bond model fit. In latex form, the fit equations are given by:

E_{FCC} (\vec{n}) = p_1 (4 \left( |x+y| + |x-y| + |x+z| + |x-z| + |z+y| +|z-y|\right)) + p_2 (8 \left( |x| + |y| + |z|\right)) + p_3 (2 ( |x+ 2y + z| + |x+2y-z| + |x-2y + z| + |x-2y-z| + |2x+y+z| + |2x+y-z| +|2x-y+z| +|2x-y-z| +|x+y+2z| +|x+y-2z| +|x-y+2z| +|x-y-2z| ) + c

E_{BCC} (\vec{n}) = p_1 (6 \left( | x+y+z| + |x+y-z| + |-x+y-z| + |x-y+z| \right)) + p_2 (8 \left( |x| + |y| + |z|\right)) + p_3 (4 \left( |x+y| + |x-y| + |x+z| + |x-z| + |z+y| +|z-y|\right)) +c.

In Python, these two fits take the following form:

def BrokenBondFCC(params, index):

import numpy
x, y, z = index
x = x / numpy.sqrt(x**2.+y**2.+z**2.)
y = y / numpy.sqrt(x**2.+y**2.+z**2.)
z = z / numpy.sqrt(x**2.+y**2.+z**2.)

return params[0]*4* (abs(x+y) + abs(x-y) + abs(x+z) + abs(x-z) + abs(z+y) + abs(z-y)) + params[1]*8*(abs(x) + abs(y) + abs(z)) + params[2]*(abs(x+2*y+z) + abs(x+2*y-z) +abs(x-2*y+z) +abs(x-2*y-z) + abs(2*x+y+z) +abs(2*x+y-z) +abs(2*x-y+z) +abs(2*x-y-z) + abs(x+y+2*z) +abs(x+y-2*z) +abs(x-y+2*z) +abs(x-y-2*z))+params[3]

def BrokenBondBCC(params, x, y, z):

import numpy
x, y, z = index
x = x / numpy.sqrt(x**2.+y**2.+z**2.)
y = y / numpy.sqrt(x**2.+y**2.+z**2.)
z = z / numpy.sqrt(x**2.+y**2.+z**2.)

return params[0]*6*(abs(x+y+z) + abs(x-y-z) + abs(x-y+z) + abs(x+y-z)) + params[1]*8*(abs(x) + abs(y) + abs(z)) + params[2]*4* (abs(x+y) + abs(x-y) + abs(x+z) + abs(x-z) + abs(z+y) + abs(z-y)) + params[3]

Test	Test Results	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Broken-bond fit of high-symmetry surface energies in bcc W v004		view	17978

VacancyFormationEnergyRelaxationVolume__TD_647413317626_001

Monovacancy formation energy and relaxation volume for cubic and hcp monoatomic crystals v001

Creators:
Contributor: efuem
Publication Year: 2023
DOI: https://doi.org/10.25950/fca89cea

Computes the monovacancy formation energy and relaxation volume for cubic and hcp monoatomic crystals.

Test	Test Results	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Monovacancy formation energy and relaxation volume for bcc W		view	219831

VacancyFormationMigration__TD_554849987965_001

Vacancy formation and migration energies for cubic and hcp monoatomic crystals v001

Creators:
Contributor: efuem
Publication Year: 2023
DOI: https://doi.org/10.25950/c27ba3cd

Computes the monovacancy formation and migration energies for cubic and hcp monoatomic crystals.

Test	Test Results	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Vacancy formation and migration energy for bcc W		view	4227068

Errors

DislocationCoreEnergyCubic__TD_452950666597_002

Test	Error Categories	Link to Error page
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [0, 0, 1] v000	other	view
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [1, 1, -2] v000	other	view
Dislocation core energy for bcc W computed at zero temperature for a set of dislocation core cutoff radii with burgers vector [0.5, 0.5, 0.5] along line direction [2, 2, 1] v000	other	view

LatticeConstantHexagonalEnergy__TD_942334626465_004

Test	Error Categories	Link to Error page
Equilibrium lattice constants for hcp W	other	view

Files

CMakeLists.txt
LICENSE
kimprovenance.edn
kimspec.edn
w_eam4.fs

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EAM_Dynamo_MarinicaVentelonGilbert_2013EAM4__MO_046576227003_000.txz	Tar+XZ	Linux and OS X archive
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This Model requires a Model Driver. Archives for the Model Driver EAM_Dynamo__MD_120291908751_005 appear below.

EAM_Dynamo__MD_120291908751_005.txz	Tar+XZ	Linux and OS X archive
EAM_Dynamo__MD_120291908751_005.zip	Zip	Windows archive

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EAM_Dynamo_MarinicaVentelonGilbert_2013EAM4__MO_046576227003_000

Verification Check Dashboard

Visualizers (in-page)

BCC Lattice Constant

Cohesive Energy Graph

Diamond Lattice Constant

Dislocation Core Energies

FCC Elastic Constants

FCC Lattice Constant

FCC Stacking Fault Energies

FCC Surface Energies

SC Lattice Constant

Cubic Crystal Basic Properties Table

Tests

Errors

Files

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