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This panel provides information on past usage of this interatomic potential (IP) powered by the OpenKIM Deep Citation framework. The word cloud indicates typical applications of the potential. The bar chart shows citations per year of this IP (bars are divided into articles that used the IP (green) and those that did not (blue)). The complete list of articles that cited this IP is provided below along with the Deep Citation determination on usage. See the Deep Citation documentation for more information.
191 Citations (143 used)
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USED (high confidence) D. Blaschke, J. Chen, S. Fensin, and B. Szajewski, “Clarifying the definition of ‘transonic’ screw dislocations,” Philosophical Magazine. 2020. link Times cited: 11 Abstract: ABSTRACT A number of recent Molecular Dynamics (MD) simulati… read moreAbstract: ABSTRACT A number of recent Molecular Dynamics (MD) simulations have demonstrated that screw dislocations in face centred cubic (fcc) metals can achieve stable steady state motion above the lowest shear wave speed ( ) which is parallel to their direction of motion (often referred to as transonic motion). This is in direct contrast to classical continuum analyses which predict a divergence in the elastic energy of the host material at a crystal geometry dependent ‘critical’ velocity . Within this work, we first demonstrate through analytic analyses that the elastic energy of the host material diverges at a dislocation velocity ( ) which is greater than , i.e. . We argue that it is this latter derived velocity ( ) which separates ‘subsonic’ and ‘supersonic’ regimes of dislocation motion in the analytic solution. In addition to our analyses, we also present a comprehensive suite of MD simulation results of steady state screw dislocation motion for a range of stresses and several cubic metals at both cryogenic and room temperatures. At room temperature, both our independent MD simulations and the earlier works find stable screw dislocation motion only below our derived . Nonetheless, in real-world polycrystalline materials cannot be interpreted as a hard limit for subsonic dislocation motion. In fact, at very low temperatures our MD simulations of Cu at 10 Kelvin confirm a recent claim in the literature that true ‘supersonic’ screw dislocations with dislocation velocities are possible at very low temperatures. read less USED (high confidence) S. C. Hu et al., “Texture evolution in nanocrystalline Ta under shock compression,” Journal of Applied Physics. 2020. link Times cited: 3 Abstract: We present systematic investigation on texture evolution in … read moreAbstract: We present systematic investigation on texture evolution in nanocrystalline Ta under planar shock wave loading at different impact velocities. Seven representative initial textures and two loading directions are studied via large-scale molecular dynamics simulations. Orientation mapping and texture analysis, including orientation distribution functions, pole figures, and inverse pole figures, are performed. Shock compression induces a ⟨ 221 ⟩ texture in nanocrystalline Ta initially with no texture, ⟨ 100 ⟩ fiber texture, { 100 } ⟨ 100 ⟩ texture, and θ + γ rolling texture via twinning, which can be traced back to grains initially with ⟨ 100 ⟩. A ⟨ 100 ⟩ texture is induced via twinning for nanocrystalline Ta initially with no texture, ⟨ 110 ⟩ fiber texture, and α + γ rolling texture and can be traced back to ⟨ 110 ⟩. Dislocation slip and grain boundary sliding lead to the movement of ⟨ 110 ⟩ toward ⟨ 111 ⟩, and the strengthening of ⟨ 100 ⟩ and ⟨ 111 ⟩ orientation densities. The generation of new textures is observed for most cases. However, no new texture is found in the ⟨ 111 ⟩ fiber texture case for shock loading parallel to the fiber, and a much slower elastic–plastic transition occurs due to the lack of deformation twinning. read less USED (high confidence) N. Zhou, K. Elkhodary, X. Huang, S. Tang, and Y. Li, “Dislocation structure and dynamics govern pop-in modes of nanoindentation on single-crystal metals,” Philosophical Magazine. 2020. link Times cited: 14 Abstract: ABSTRACT There are two types of pop-in mode that have been w… read moreAbstract: ABSTRACT There are two types of pop-in mode that have been widely observed in nanoindentation experiments: the single pop-in, and the successive pop-in modes. Here we employ the molecular dynamics (MD) modelling to simulate nanoindentation for three face-centred cubic (FCC) metals, including Al, Cu and Ni, and two body-centred cubic (BCC) metals, such as Fe and Ta. We aim to examine the deformation mechanisms underlying these pop-in modes. Our simulation results indicate that the dislocation structures formed in single crystals during nanoindentation are mainly composed of half prismatic dislocation loops. These half prismatic dislocation loops in FCC metals are primarily constituted of extended dislocations. Lomer–Cottrell locks that result from the interactions between these extended dislocations can resist the slipping of half dislocation loops. These locks can build up the elastic energy that is needed to activate the nucleation of new half dislocation loops. A repetition of this sequence results in successive pop-in events in Al and other FCC metals. Conversely, the half prismatic dislocation loops that form in BCC metals after first pop-in are prone to slip into the bulk, which sustains plastic indentation process after first pop-in and prevents subsequent pop-ins. We thus conclude that pop-in modes are correlated with lattice structures during nanoindentation, regardless of their crystal orientations. read less USED (high confidence) G. Lerma, B. Verschueren, B. Gurrutxaga-Lerma, and J. Verschueren, “Generalized Kanzaki force field of extended defects in crystals with applications to the modeling of edge dislocations,” Physical Review Materials. 2019. link Times cited: 4 Abstract: The Kanzaki forces and their associated multipolar moments a… read moreAbstract: The Kanzaki forces and their associated multipolar moments are standard ways of representing point defects in an atomistically informed way in the continuum. In this article, the Kanzaki force approach is extended to other crystalline defects. The article shows how the resulting Kanzaki force fields are to be computed for any general extended defect by first computing the relaxed defect’s structure and then defining an affine mapping between the said defect structure and the original perfect lattice. This methodology can be employed to compute the Kanzaki force field of any mass-conserving defect, including dislocations, grain and twin boundaries, or cracks. Particular focus is then placed on straight edge dislocation in face-centered cubic (fcc) and body-centered cubic (bcc) pure metals, which are studied along different crystallographic directions. The particular characteristics of these force fields are discussed, drawing a distinction between the slip Kanzaki force field associated with the Volterra disregistry that characterizes the dislocation, and the core Kanzaki force field associated with the specific topology of the dislocation’s core. The resulting force fields can be employed to create elastic models of the dislocation that, unlike other regularization procedures, offer a geometrically true representation of the core and the elastic fields in its environs, capturing all three-dimensional effects associated with the core. DOI: 10.1103/PhysRevMaterials read less USED (high confidence) J. Chen, E. Hahn, A. Dongare, and S. Fensin, “Understanding and predicting damage and failure at grain boundaries in BCC Ta,” Journal of Applied Physics. 2019. link Times cited: 35 Abstract: Understanding the effect of grain boundaries (GBs) on the de… read moreAbstract: Understanding the effect of grain boundaries (GBs) on the deformation and spall behavior is critical to designing materials with tailored failure responses under dynamic loading. This understanding is hampered by the lack of in situ imaging capability with the optimum spatial and temporal resolution during dynamic experiments, as well as by the scarcity of a systematic data set that correlates boundary structure to failure, especially in BCC metals. To fill in this gap in the current understanding, molecular dynamics simulations are performed on a set of 74 bi-crystals in Ta with a [110] symmetric tilt axis. Our results show a correlation between GB misorientation angle and spall strength and also highlight the importance of GB structure itself in determining the spall strength. Specifically, we find a direct correlation between the ability of the GB to plasticity deform through slip/twinning and its spall strength. Additionally, a change in the deformation mechanism from dislocation-meditated to twinning-dominated plasticity is observed as a function of misorientation angles, which results in lowered spall strengths for high-angle GBs.Understanding the effect of grain boundaries (GBs) on the deformation and spall behavior is critical to designing materials with tailored failure responses under dynamic loading. This understanding is hampered by the lack of in situ imaging capability with the optimum spatial and temporal resolution during dynamic experiments, as well as by the scarcity of a systematic data set that correlates boundary structure to failure, especially in BCC metals. To fill in this gap in the current understanding, molecular dynamics simulations are performed on a set of 74 bi-crystals in Ta with a [110] symmetric tilt axis. Our results show a correlation between GB misorientation angle and spall strength and also highlight the importance of GB structure itself in determining the spall strength. Specifically, we find a direct correlation between the ability of the GB to plasticity deform through slip/twinning and its spall strength. Additionally, a change in the deformation mechanism from dislocation-meditated to twinning... read less USED (high confidence) P. Heighway, D. McGonegle, N. Park, A. Higginbotham, and J. Wark, “Molecular dynamics simulations of grain interactions in shock-compressed highly textured columnar nanocrystals,” Physical Review Materials. 2019. link Times cited: 7 Abstract: While experimental and computational studies abound demonstr… read moreAbstract: While experimental and computational studies abound demonstrating the diverse range of phenomena caused by grain interactions under quasistatic loading conditions, far less attention has been given to these interactions under the comparatively dramatic conditions of shock compression. The consideration of grain interactions is essential within the context of contemporary shock-compression experiments that exploit the distinctive x-ray diffraction patterns of highly textured (and therefore strongly anisotropic) targets in order to interrogate local structural evolution. We present here a study of grain interaction effects in shock-compressed, body-centered cubic tantalum nanocrystals characterized by a columnar geometry and a strong fiber texture using large-scale molecular dynamics simulations. Our study reveals that contiguous grains deform cooperatively in directions perpendicular to the shock, driven by the gigapascal-scale stress gradients induced over their boundaries by the uniaxial compression, and in so doing are able to reach a state of reduced transverse shear stress. We compare the extent of this relaxation for two different columnar geometries (distinguished by their square or hexagonal cross-sections), and quantify the attendant change in the transverse elastic strains. We further show that cooperative deformation is able to replace ordinary plastic deformation mechanisms at lower shock pressures, and, under certain conditions, activate new mechanisms at higher pressures. read less USED (high confidence) Y. Y. Zhang, M. Tang, Y. Cai, J. E, and S. Luo, “Deducing density and strength of nanocrystalline Ta and diamond under extreme conditions from X-ray diffraction.,” Journal of synchrotron radiation. 2019. link Times cited: 3 Abstract: In situ X-ray diffraction with advanced X-ray sources offers… read moreAbstract: In situ X-ray diffraction with advanced X-ray sources offers unique opportunities for investigating materials properties under extreme conditions such as shock-wave loading. Here, Singh's theory for deducing high-pressure density and strength from two-dimensional (2D) diffraction patterns is rigorously examined with large-scale molecular dynamics simulations of isothermal compression and shock-wave compression. Two representative solids are explored: nanocrystalline Ta and diamond. Analysis of simulated 2D X-ray diffraction patterns is compared against direct molecular dynamics simulation results. Singh's method is highly accurate for density measurement (within 1%) and reasonable for strength measurement (within 10%), and can be used for such measurements on nanocrystalline and polycrystalline solids under extreme conditions (e.g. in the megabar regime). read less USED (high confidence) E. Fransson, F. Eriksson, and P. Erhart, “Efficient construction of linear models in materials modeling and applications to force constant expansions,” npj Computational Materials. 2019. link Times cited: 21 USED (high confidence) X. Fan, D. Pan, and M. Li, “Melting of bcc crystal Ta without the Lindemann criterion,” Journal of Physics: Condensed Matter. 2019. link Times cited: 9 Abstract: Understanding of melting is deeply rooted in the Lindemann c… read moreAbstract: Understanding of melting is deeply rooted in the Lindemann criterion which predicts that the transition occurs when the mean vibrational atomic displacement reaches a universal value. The criterion also finds its way in atomic description of kinetics of various structural phase transitions involving liquid and amorphous phases. Here we show using atomistic modeling in bcc crystal tantalum that neither the universal displacement exists nor melting occurs at the anticipated value from the Lindemann criterion. Instead, before and at melting a series of strongly correlated atomic diffusional motions are set in with the atomic displacement far more complicated than that predicted by Lindemann based on independent atomic vibrations. The displacement leads to formation of new extended atomic configurations composed of lattice chains and loops of Ta atoms still residing on the crystal lattice. It is the proliferation of these lattice chains that leads to melting. read less USED (high confidence) W. Yang et al., “Micro-Mechanical Response of Ultrafine Grain and Nanocrystalline Tantalum,” EngRN: Materials Chemistry (Topic). 2019. link Times cited: 4 Abstract: In order to investigate the effect of grain boundaries on th… read moreAbstract: In order to investigate the effect of grain boundaries on the mechanical response in the micrometer and submicrometer levels, complementary experiments and molecular dynamics simulations were conducted on a model bcc metal, tantalum. Microscale pillar experiments (diameters of 1 and 2 μm) with a grain size of ∼ 100-200 nm revealed a mechanical response characterized by a yield stress of ∼1,500 MPa. The hardening of the structure is reflected in the increase in the flow stress to 1,700 MPa at a strain of ∼0.35. Molecular dynamics simulations were conducted for nanocrystalline tantalum with grain sizes in the range of 20-50 nm and pillar diameters in the same range. The yield stress was approximately 6,000 MPa for all specimens and the maximum of the stress-strain curves occurred at a strain of 0.07. Beyond that strain, the material softened because of its inability to store dislocations. The experimental results did not show a significant size dependence of yield stress on pillar diameter (equal to 1 and 2 um), which is attributed to the high ratio between pillar diameter and grain size (∼10-20). This behavior is quite different from that in monocrystalline specimens where dislocation ‘starvation’ leads to a significant size dependence of strength. The ultrafine grains exhibit clear ‘pancaking’ upon being plastically deformed, with an increase in dislocation density. The plastic deformation is much more localized for the single crystals than for the nanocrystalline specimens, an observation made in both modeling and experiments. In the molecular dynamics simulations, the ratio of pillar diameter (20-50 nm) to grain size was in the range 0.2 to 2, and a much greater dependence of yield stress to pillar diameter was observed. A critical result from this work is the demonstration that the important parameter in establishing the overall deformation is the ratio between the grain size and pillar diameter; it governs the deformation mode as well as surface sources and sinks, which are only important when the grain size is of the same order as the pillar diameter. read less USED (high confidence) T. Remington et al., “Spall strength dependence on grain size and strain rate in tantalum,” Acta Materialia. 2018. link Times cited: 88 USED (high confidence) M. Sliwa et al., “Femtosecond X-Ray Diffraction Studies of the Reversal of the Microstructural Effects of Plastic Deformation during Shock Release of Tantalum.,” Physical review letters. 2018. link Times cited: 40 Abstract: We have used femtosecond x-ray diffraction to study laser-sh… read moreAbstract: We have used femtosecond x-ray diffraction to study laser-shocked fiber-textured polycrystalline tantalum targets as the 37-253 GPa shock waves break out from the free surface. We extract the time and depth-dependent strain profiles within the Ta target as the rarefaction wave travels back into the bulk of the sample. In agreement with molecular dynamics simulations, the lattice rotation and the twins that are formed under shock compression are observed to be almost fully eliminated by the rarefaction process. read less USED (high confidence) W. Li, K. Li, K. Fan, D.-xing Zhang, and W.-dong Wang, “Temperature and Pressure Dependences of the Elastic Properties of Tantalum Single Crystals Under <100> Tensile Loading: A Molecular Dynamics Study,” Nanoscale Research Letters. 2018. link Times cited: 10 USED (high confidence) R. Kositski, D. Steinberger, S. Sandfeld, and D. Mordehai, “Shear relaxation behind the shock front in 110 molybdenum – From the atomic scale to continuous dislocation fields,” Computational Materials Science. 2018. link Times cited: 15 USED (high confidence) Y. Cai, Z. Y. Zhong, M. Tang, X. Zhu, L. Wang, and S. Luo, “Texture of nanocrystalline solids: atomic scale characterization and applications,” Journal of Applied Crystallography. 2018. link Times cited: 5 Abstract: A methodology is presented to characterize the crystallograp… read moreAbstract: A methodology is presented to characterize the crystallographic texture of atomic configurations on the basis of Euler angles. Texture information characterized by orientation map, orientation distribution function, texture index, pole figure and inverse pole figure is obtained. The paper reports the construction and characterization of the texture of nanocrystalline configurations with different grain numbers, grain sizes and percentages of preferred orientation. The minimum grain number for texture-free configurations is ∼2500. The effect of texture on deducing grain size from simulated X-ray diffraction curves is also explored as an application case of texture analysis. In addition, molecular dynamics simulations are performed on initially texture-free nanocrystalline Ta under shock-wave loading, which shows a 〈001〉 + 〈111〉 double fiber texture after shock-wave compression. read less USED (high confidence) T. White et al., “Identifying deformation mechanisms in molecular dynamics simulations of laser shocked matter,” J. Comput. Phys. 2017. link Times cited: 1 USED (high confidence) C. Huang, X. Peng, B. Yang, Y. Zhao, S. Weng, and T. Fu, “Investigation of Interaction between Dislocation Loop and Coherent Twin Boundary in BCC Ta Film during Nanoindentation,” Nanomaterials. 2017. link Times cited: 4 Abstract: In this work, the interaction between dislocation loop (DL) … read moreAbstract: In this work, the interaction between dislocation loop (DL) and coherent twin boundary (CTB) in a body-centered cubic (BCC) tantalum (Ta) film during nanoindentation was investigated with molecular dynamics (MD) simulation. The formation and propagation of <111> full DLs in the nanotwinned (nt) Ta film during the indentation was observed, and it was found that CTB can strongly affect the stress distribution in the Ta film, and thus change the motion and type of dislocations. There are three kinds of mechanisms for the interaction between DL and CTB in a twinned BCC Ta film: (i) dislocation absorption, (ii) dislocation desorption, and (iii) direct slip transmission. The nucleation of twin boundary dislocations and the formation of the steps in CTB were also observed during the indentation. The mechanisms presented in this work can provide atomic images for understanding the plastic deformation of BCC metals with mirror-symmetry grain boundary structures, and provide available information for the evaluation and design of high-performance nt BCC metallic thin film coatings. read less USED (high confidence) O. Donaldson, W. Wang, K. Hattar, and J. Trelewicz, “Impurity stabilization of nanocrystalline grains in pulsed laser deposited tantalum,” Journal of Materials Research. 2017. link Times cited: 4 Abstract: Thermal stability of pulsed laser deposited (PLD) nanocrysta… read moreAbstract: Thermal stability of pulsed laser deposited (PLD) nanocrystalline tantalum was explored through in situ transmission electron microscopy (TEM) annealing over the temperature range of 800–1200 °C. The evolution of the nanostructure was characterized using grain size distributions collectively with electron diffraction analysis and electron energy loss spectroscopy (EELS). Grain growth dynamics were further explored through molecular dynamics (MD) simulations of columnar tantalum nanostructures. The as-deposited grain size of 32 nm increased by only 18% at 1200 °C, i.e., 40% the melting point of tantalum, conflicting with the MD simulations that demonstrated extensive grain coalescence above 1000 °C. Furthermore, the grain size remained stable through the reversible α-to-β phase transition near 800 °C, which is often accompanied by grain growth in nanostructured tantalum. The EELS analysis confirmed the presence of oxygen impurities in the as-deposited films, indicating that impurity stabilization of grain boundaries was responsible for the exceptional thermal stability of PLD nanocrystalline tantalum. read less USED (high confidence) E. Hahn, T. Germann, R. Ravelo, J. Hammerberg, and M. Meyers, “On the ultimate tensile strength of tantalum,” Acta Materialia. 2017. link Times cited: 78 USED (high confidence) E. Hahn, S. Fensin, T. Germann, and M. Meyers, “Symmetric tilt boundaries in body-centered cubic tantalum,” Scripta Materialia. 2016. link Times cited: 40 USED (high confidence) Z. Shi and C. V. Singh, “Competing twinning mechanisms in body-centered cubic metallic nanowires,” Scripta Materialia. 2016. link Times cited: 39 USED (high confidence) C. Ruestes, E. Bringa, R. Rudd, B. Remington, T. Remington, and M. Meyers, “Probing the character of ultra-fast dislocations,” Scientific Reports. 2015. link Times cited: 35 USED (high confidence) R. Cao, Y. Deng, and C. Deng, “Hardening and crystallization in monatomic metallic glass during elastic cycling,” Journal of Materials Research. 2015. link Times cited: 9 Abstract: While conventional metallic glass (MG) is usually an alloy t… read moreAbstract: While conventional metallic glass (MG) is usually an alloy that contains at least two types of different elements, monatomic metallic glass (MMG) in body-centered cubic metals has recently been vitrified experimentally through ultrafast quenching. In this research, MMG in Ta was vitrified by molecular dynamics simulations and used as a model system to explore the atomistic mechanism of hardening in MG under cyclic loading well below the yield point. It was found that significant structural ordering was caused during the elastic cycling without accumulating apparent plastic strain, which ultimately led to the crystallization of MG that has been long conjectured but rarely directly proved before. It was also revealed that tensile stresses were more likely to induce structural ordering and crystallization in MG than compressive stresses. read less USED (high confidence) T. Remington et al., “Plastic deformation in nanoindentation of tantalum: A new mechanism for prismatic loop formation,” Acta Materialia. 2014. link Times cited: 129 USED (high confidence) C. Ruestes, E. Bringa, A. Stukowski, J. R. Nieva, Y. Tang, and M. Meyers, “Plastic deformation of a porous bcc metal containing nanometer sized voids,” Computational Materials Science. 2014. link Times cited: 43 USED (high confidence) L. Wang, F. Zhao, Y. Cai, Q. An, and S. Luo, “Grain boundary orientation effects on deformation of Ta bicrystal nanopillars under high strain-rate compression,” Journal of Applied Physics. 2014. link Times cited: 28 Abstract: We investigate grain boundary (GB) orientation effects on de… read moreAbstract: We investigate grain boundary (GB) orientation effects on deformation of Ta bicrystal nanopillars under high strain-rate, uniaxial compression with molecular dynamics simulations. The GB is of the ⟨110⟩90° twist grain boundary type. We vary the angle between the GB normal and the loading direction (θ) in the range of 0°–90° while keeping the GB type unchanged. The GB orientation has strong effects on deformation mechanism, yield stress, failure strain, and dynamics, due to the combined effects of Schmid factors in constituent crystals and resolved shear stress on the GB plane. Single crystal plasticity and GB deformation are competing factors, and the GB-initiated deformation mechanisms (stacking faults vs. twinning, and GB sliding) depend on the local stress level around the GB. The large Schmid factors in constituent single crystals for θ=0° lead to twinning in the single crystals and the lowest yield stress; the ensuing GB deformation is achieved via stacking fault formation due to premature stress relaxation. However, nanopillar deformation in the cases of higher angles is dominated by GB deformation largely in the form of twinning, driven by enhanced stress buildup. GB-initiated deformation in the high Schmid factor nanocrystal precedes and may drive that in the low Schmid factor nanocrystal. The details of twin/stacking fault nucleation and growth/shrinking, twin-twin interaction, and twin-GB interaction are also discussed. read less USED (low confidence) J. A. Vita and D. Trinkle, “Spline-based neural network interatomic potentials: blending classical and machine learning models,” ArXiv. 2023. link Times cited: 0 Abstract: While machine learning (ML) interatomic potentials (IPs) are… read moreAbstract: While machine learning (ML) interatomic potentials (IPs) are able to achieve accuracies nearing the level of noise inherent in the first-principles data to which they are trained, it remains to be shown if their increased complexities are strictly necessary for constructing high-quality IPs. In this work, we introduce a new MLIP framework which blends the simplicity of spline-based MEAM (s-MEAM) potentials with the flexibility of a neural network (NN) architecture. The proposed framework, which we call the spline-based neural network potential (s-NNP), is a simplified version of the traditional NNP that can be used to describe complex datasets in a computationally efficient manner. We demonstrate how this framework can be used to probe the boundary between classical and ML IPs, highlighting the benefits of key architectural changes. Furthermore, we show that using spline filters for encoding atomic environments results in a readily interpreted embedding layer which can be coupled with modifications to the NN to incorporate expected physical behaviors and improve overall interpretability. Finally, we test the flexibility of the spline filters, observing that they can be shared across multiple chemical systems in order to provide a convenient reference point from which to begin performing cross-system analyses. read less USED (low confidence) 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 USED (low confidence) Y.-F. Wu, W. Yu, and S. Shen, “Developing an analytical bond-order potential for Hf/Nb/Ta/Zr/C system using machine learning global optimization,” Ceramics International. 2023. link Times cited: 0 USED (low confidence) A. H. M. Faisal and C. Weinberger, “Nucleation of Extended Defects in BCC Transition Metals,” International Journal of Plasticity. 2023. link Times cited: 0 USED (low confidence) X. Li, Z. Zhang, and J. Wang, “Deformation twinning in body-centered cubic metals and alloys,” Progress in Materials Science. 2023. link Times cited: 4 USED (low confidence) Q. Liu, Y. F. Xu, S. C. Hu, Y. X. Li, Y. Cai, and S. Luo, “Multiple elastic shock waves in cubic single crystals,” Shock Waves. 2023. link Times cited: 0 USED (low confidence) Z. Xu and Y. Ni, “The effect of kink-like defects on the twin boundaries of nanotwinned Ta under nanoindentation,” Applied Surface Science. 2023. link Times cited: 1 USED (low confidence) Y.-F. Wu, W. Yu, and S. Shen, “Developing a variable charge potential for Hf/Nb/Ta/Ti/Zr/O system via machine learning global optimization,” Materials & Design. 2023. link Times cited: 1 USED (low confidence) S. Wang et al., “The anomalous annealing hardening behaviors in commercial pure Tantalum foil,” Materials Science and Engineering: A. 2023. link Times cited: 0 USED (low confidence) S. Galitskiy, A. Mishra, and A. Dongare, “Modeling Shock-induced Void Collapse in Single-crystal Ta Systems at the Mesoscales,” International Journal of Plasticity. 2023. link Times cited: 2 USED (low confidence) Y. Li, D. Yang, and W. Qiang, “Atomistic simulations of enhanced irradiation resistance and defect properties in body-centered cubic W-V-Cr and W-Ta-V alloys,” Journal of Alloys and Compounds. 2023. link Times cited: 2 USED (low confidence) Q. Bao et al., “Influence of kinetic effect on interaction between edge dislocation and irradiated dislocation loops in BCC Tantalum,” International Journal of Plasticity. 2023. link Times cited: 3 USED (low confidence) D. Bishara and S. Li, “A machine-learning aided multiscale homogenization model for crystal plasticity: application for face-centered cubic single crystals,” Computational Mechanics. 2023. link Times cited: 2 USED (low confidence) N. Amadou, A. R. A. Abdoulaye, T. de Rességuier, and A. Dragon, “Strain-Rate Dependence of Plasticity and Phase Transition in [001]-Oriented Single-Crystal Iron,” Crystals. 2023. link Times cited: 1 Abstract: Non-equilibrium molecular dynamics simulations have been use… read moreAbstract: Non-equilibrium molecular dynamics simulations have been used to investigate strain-rate dependence of plasticity and phase transition in [001]-oriented single-crystal iron under ramp compression. Here, plasticity is governed by deformation twinning, in which kinetics is tightly correlated with the loading rate. Over the investigated range of strain rates, a hardening-like effect is found to shift the onset of the structural bcc-to-hcp phase transformation to a high, almost constant stress during the ramp compression regime. However, when the ramp evolves into a shock wave, the bcc–hcp transition is triggered whenever the strain rate associated with the plastic deformation reaches some critical value, which depends on the loading rate, leading to a constitutive functional dependence of the transition onset stress on the plastic deformation rate, which is in overall consistence with the experimental data under laser compression. read less USED (low confidence) M. B. Salman, M. Park, and M. Banisalman, “Atomistic Study for the Tantalum and Tantalum–Tungsten Alloy Threshold Displacement Energy under Local Strain,” International Journal of Molecular Sciences. 2023. link Times cited: 1 Abstract: The threshold displacement energy (TDE) is an important meas… read moreAbstract: The threshold displacement energy (TDE) is an important measure of the extent of a material’s radiation damage. In this study, we investigate the influence of hydrostatic strains on the TDE of pure tantalum (Ta) and Ta–tungsten (W) alloy with a W content ranging from 5% to 30% in 5% intervals. Ta–W alloy is commonly used in high-temperature nuclear applications. We found that the TDE decreased under tensile strain and increased under compressive strain. When Ta was alloyed with 20 at% W, the TDE increased by approximately 15 eV compared to pure Ta. The directional-strained TDE (Ed,i) appears to be more influenced by complex 〈i j k〉 directions rather than soft directions, and this effect is more prominent in the alloyed structure than in the pure one. Our results suggest that radiation defect formation is enhanced by tensile strain and suppressed by compressive strain, in addition to the effects of alloying. read less USED (low confidence) J. Wang et al., “Unraveling the plasticity performance and melting in single crystal tantalum damaged by shock compression,” Engineering Fracture Mechanics. 2022. link Times cited: 5 USED (low confidence) J. Wang, F. Wang, X. Wu, Z. Xu, and X. Yang, “Orientation-induced anisotropy of plasticity and damage behavior in monocrystalline tantalum under shock compression,” Vacuum. 2022. link Times cited: 3 USED (low confidence) J. Li and Q. An, “Quasiplastic Deformation in Shocked Nanocrystalline Boron Carbide: Grain Boundary Sliding and Local Amorphization,” Journal of the European Ceramic Society. 2022. link Times cited: 7 USED (low confidence) J. Varillas and L. Rondoni, “Work and Thermal Fluctuations in Crystal Indentation under Deterministic and Stochastic Thermostats: The Role of System–Bath Coupling,” Entropy. 2022. link Times cited: 0 Abstract: The Jarzynski equality (JE) was originally derived under the… read moreAbstract: The Jarzynski equality (JE) was originally derived under the deterministic Hamiltonian formalism, and later, it was demonstrated that stochastic Langevin dynamics also lead to the JE. However, the JE has been verified mainly in small, low-dimensional systems described by Langevin dynamics. Although the two theoretical derivations apparently lead to the same expression, we illustrate that they describe fundamentally different experimental conditions. While the Hamiltonian framework assumes that the thermal bath producing the initial canonical equilibrium switches off for the duration of the work process, the Langevin bath effectively acts on the system. Moreover, the former considers an environment with which the system may interact, whereas the latter does not. In this study, we investigate the effect of the bath on the measurable quantity of the JE through molecular dynamics simulations of crystal nanoindentation employing deterministic and stochastic thermostats. Our analysis shows that the distributions of the kinetic energy and the mechanical work produced during the indentation processes are affected by the interaction between the system and the thermostat baths. As a result, the type of thermostatting has also a clear effect on the left-hand side of the JE, which enables the estimation of the free-energy difference characterizing the process. read less USED (low confidence) D. F. Rojas, M. Isiet, and M. Ponga, “Dynamic recrystallization in face-centered cubic particles during high-velocity impacts,” Mechanics of Materials. 2022. link Times cited: 6 USED (low confidence) A. Mishra et al., “Virtual texture analysis to investigate the deformation mechanisms in metal microstructures at the atomic scale,” Journal of Materials Science. 2022. link Times cited: 8 USED (low confidence) J. Varillas, G. Ciccotti, J. Alcalá, and L. Rondoni, “Jarzynski equality on work and free energy: Crystal indentation as a case study.,” The Journal of chemical physics. 2022. link Times cited: 3 Abstract: Mathematical relations concerning particle systems require k… read moreAbstract: Mathematical relations concerning particle systems require knowledge of the applicability conditions to become physically relevant and not merely formal. We illustrate this fact through the analysis of the Jarzynski equality (JE), whose derivation for Hamiltonian systems suggests that the equilibrium free-energy variations can be computational or experimentally determined in almost any kind of non-equilibrium processes. This apparent generality is surprising in a mechanical theory. Analytically, we show that the quantity called "work" in the Hamiltonian derivation of the JE is neither a thermodynamic quantity nor mechanical work, except in special circumstances to be singularly assessed. Through molecular dynamics simulations of elastic and plastic deformations induced via nano-indentation of crystalline surfaces that fall within the formal framework of the JE, we illustrate that the JE cannot be verified and that the results of this verification are process dependent. read less USED (low confidence) M. Tang, C. Li, Y. Cai, and S. Luo, “Deformation twinning to dislocation slip transition in single-crystal tantalum under dynamic compression,” Journal of Materials Science. 2022. link Times cited: 0 USED (low confidence) W. Li et al., “Deformation Mechanism of Depositing Amorphous Cu-Ta Alloy Film via Nanoindentation Test,” Nanomaterials. 2022. link Times cited: 2 Abstract: As a representative of immiscible alloy systems, the Cu-Ta s… read moreAbstract: As a representative of immiscible alloy systems, the Cu-Ta system was the research topic because of its potential application in industry, military and defense fields. In this study, an amorphous Cu-Ta alloy film was manufactured through magnetron sputter deposition, which was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties of Cu-Ta film were detected by the nanoindentation method, which show that the elastic modulus of Cu3.5Ta96.5 is 156.7 GPa, and the hardness is 14.4 GPa. The nanoindentation process was also simulated by molecular dynamic simulation to indicate the deformation mechanism during the load-unload stage. The simulation results show that the structure <0,2,8,4> and <0,2,8,5> Voronoi cells decreased by 0.1% at 50 Ps and then remained at this value during the nanoindentation process. In addition, the number of dislocations vary rapidly with the depth between indenter and surface. Based on the experimental and simulation results, the Voronoi structural changes and dislocation motions are the key reasons for the crystallization of amorphous alloys when loads are applied. read less USED (low confidence) B. Hamilton and A. Strachan, “Many-Body Mechanochemistry: Intra-molecular Strain in Condensed Matter Chemistry,” Physical Review Materials. 2022. link Times cited: 8 Abstract: Mechanical forces acting on atoms or molecular groups can al… read moreAbstract: Mechanical forces acting on atoms or molecular groups can alter chemical kinetics and decomposition paths. So called mechanochemistry has been proposed to influence a variety of processes, from the formation of prebiotic compounds during planetary collisions to the shock-induced initiation of explosives. It has also been harnessed in various engineering applications such as mechanophores and ball milling in industrial applications. Experimental and computational tools designed to characterize the effect of mechanics on chemistry have focused exclusively on simple linear forces between pairs of atoms or molecular groups. However, the mechanical loading in condensed matter systems is significantly more complex and involves many-body deformations. Therefore, we propose a methodology to characterize the effect of many-body intra-molecular strains on decomposition kinetics and reaction pathways. We combine four-body external potentials with reactive molecular dynamics and show that many body strains that mimic those observed in condensed matter encourage bond rupture in a spiropyran mechanophore and accelerate thermal decomposition of condensed TATB, an energetic material. The approach is generalizable to a variety of systems and can be used in conjunction with ab initio molecular dynamics, and the two examples utilized here illustrates both the versatility of the method and the importance of many-body mechanochemistry. read less USED (low confidence) E. Mareev and F. Potemkin, “Dynamics of Ultrafast Phase Transitions in (001) Si on the Shock-Wave Front,” International Journal of Molecular Sciences. 2022. link Times cited: 3 Abstract: We demonstrate an ultrafast (<0.1 ps) reversible phase trans… read moreAbstract: We demonstrate an ultrafast (<0.1 ps) reversible phase transition in silicon (Si) under ultrafast pressure loading using molecular dynamics. Si changes its structure from cubic diamond to β-Sn on the shock-wave front. The phase transition occurs when the shock-wave pressure exceeds 11 GPa. Atomic volume, centrosymmetry, and the X-ray-diffraction spectrum were revealed as effective indicators of phase-transition dynamics. The latter, being registered in actual experimental conditions, constitutes a breakthrough in the path towards simple X-ray optical cross-correlation and pump-probe experiments. read less USED (low confidence) Y. Wang, X.-guo Zeng, X. Yang, and T. Xu, “Shock-induced spallation in single-crystalline tantalum at elevated temperatures through molecular dynamics modeling,” Computational Materials Science. 2022. link Times cited: 9 USED (low confidence) Q. Bao, M. Huang, Y. Zhu, L. Zhao, and Z. Li, “Abnormal interactions between high-speed edge dislocation and microvoid in BCC metals,” International Journal of Plasticity. 2022. link Times cited: 12 USED (low confidence) P. Li et al., “Crystallographic-orientation-dependence plasticity of niobium under shock compressions,” International Journal of Plasticity. 2022. link Times cited: 8 USED (low confidence) Z. Jian et al., “Shock-induced plasticity and phase transformation in single crystal magnesium: an interatomic potential and non-equilibrium molecular dynamics simulations,” Journal of Physics: Condensed Matter. 2021. link Times cited: 8 Abstract: An effective and reliable Finnis–Sinclair (FS) type potentia… read moreAbstract: An effective and reliable Finnis–Sinclair (FS) type potential is developed for large-scale molecular dynamics (MD) simulations of plasticity and phase transition of magnesium (Mg) single crystals under high-pressure shock loading. The shock-wave profiles exhibit a split elastic–inelastic wave in the [0001]HCP shock orientation and a three-wave structure in the [10-10]HCP and [-12-10]HCP directions, namely, an elastic precursor, a followed plastic front, and a phase-transition front. The shock Hugoniot of the particle velocity (U p) vs the shock velocity (U s) of Mg single crystals in three shock directions under low shock strength reveals apparent anisotropy, which vanishes with increasing shock strength. For the [0001]HCP shock direction, the amorphization caused by strong atomic strain plays an important role in the phase transition and allows for the phase transition from an isotropic stressed state to the product phase. The reorientation in the shock directions [10-10]HCP and [-12-10]HCP, as the primary plasticity deformation, leads to the compressed hexagonal close-packed (HCP) phase and reduces the phase-transition threshold pressure. The phase-transition pathway in the shock direction [0001]HCP includes a preferential contraction strain along the [0001]HCP direction, a tension along [-12-10]HCP direction, an effective contraction and shear along the [10-10]HCP direction. For the [10-10]HCP and [-12-10]HCP shock directions, the phase-transition pathway consists of two steps: a reorientation and the subsequent transition from the reorientation hexagonal close-packed phase (RHCP) to the body-centered cubic (BCC). The orientation relationships between HCP and BCC are (0001)HCP ⟨-12-10⟩HCP // {110}BCC ⟨001⟩BCC. Due to different slipping directions during the phase transition, three variants of the product phase are observed in the shocked samples, accompanied by three kinds of typical coherent twin-grain boundaries between the variants. The results indicate that the highly concentrated shear stress leads to the crystal lattice instability in the elastic precursor, and the plasticity or the phase transition relaxed the shear stress. read less USED (low confidence) Z. R. Liu, B. Yao, and R. F. Zhang, “SPaMD studio: An integrated platform for atomistic modeling, simulation, analysis, and visualization,” Computational Materials Science. 2021. link Times cited: 7 USED (low confidence) Y. Yuan et al., “Three-dimensional atomic packing in amorphous solids with liquid-like structure,” Nature Materials. 2021. link Times cited: 36 USED (low confidence) X. Zhang, Y. Deng, J. Chen, and W. Hu, “Study on the effect of non-centrosymmetric orientation in shocked and ramp compressed α iron,” Materials Today Communications. 2021. link Times cited: 1 USED (low confidence) S. Mishra, K. V. Reddy, and S. Pal, “Impact of crystalline–amorphous interface on shock response of metallic glass Al90Sm10/crystalline Al nanolaminates,” Applied Physics A. 2021. link Times cited: 3 USED (low confidence) J. Varillas, J. Očenášek, J. Torner, and J. Alcalá, “Understanding imprint formation, plastic instabilities and hardness evolutions in FCC, BCC and HCP metal surfaces,” Acta Materialia. 2021. link Times cited: 25 USED (low confidence) D.-S. Wu, K. Chen, Y. Zhu, L. Zhao, M. Huang, and Z. Li, “Unveiling grain size effect on shock-induced plasticity and its underlying mechanisms in nano-polycrystalline Ta,” Mechanics of Materials. 2021. link Times cited: 6 USED (low confidence) A. H. M. Faisal and C. Weinberger, “Modeling twin boundary structures in body centered cubic transition metals,” Computational Materials Science. 2021. link Times cited: 6 USED (low confidence) K. A. H. A. Mahmud, F. Hasan, M. I. Khan, and A. Adnan, “Shock-Induced Damage Mechanism of Perineuronal Nets,” Biomolecules. 2021. link Times cited: 4 Abstract: The perineuronal net (PNN) region of the brain’s extracellul… read moreAbstract: The perineuronal net (PNN) region of the brain’s extracellular matrix (ECM) surrounds the neural networks within the brain tissue. The PNN is a protective net-like structure regulating neuronal activity such as neurotransmission, charge balance, and action potential generation. Shock-induced damage of this essential component may lead to neuronal cell death and neurodegenerations. The shock generated during a vehicle accident, fall, or improvised device explosion may produce sufficient energy to damage the structure of the PNN. The goal is to investigate the mechanics of the PNN in reaction to shock loading and to understand the mechanical properties of different PNN components such as glycan, GAG, and protein. In this study, we evaluated the mechanical strength of PNN molecules and the interfacial strength between the PNN components. Afterward, we assessed the PNN molecules’ damage efficiency under various conditions such as shock speed, preexisting bubble, and boundary conditions. The secondary structure altercation of the protein molecules of the PNN was analyzed to evaluate damage intensity under varying shock speeds. At a higher shock speed, damage intensity is more elevated, and hyaluronan (glycan molecule) is most likely to break at the rigid junction. The primary structure of the protein molecules is least likely to fail. Instead, the molecules’ secondary bonds will be altered. Our study suggests that the number of hydrogen bonds during the shock wave propagation is reduced, which leads to the change in protein conformations and damage within the PNN structure. As such, we found a direct connection between shock wave intensity and PNN damage. read less USED (low confidence) T. Sun and Y. Feng, “Shock-induced melting of two-dimensional Yukawa systems from T H − P H Hugoniot curves,” Physics of Plasmas. 2021. link Times cited: 4 Abstract: The T H − P H Hugoniot curves of compressional shocks in 2D … read moreAbstract: The T H − P H Hugoniot curves of compressional shocks in 2D Yukawa systems are derived from the combination of the Rankine–Hugoniot relation around the shock front and the universal relationship for the temperature in the postshock region. From the equation of state of 2D Yukawa liquids, the equilibrium melting curve for 2D Yukawa systems is derived using the two variables of the temperature T and the pressure P. It is found that the obtained T H − P H Hugoniot curves are intercepted by the equilibrium melting curve, indicating the existence of shock-induced phase transition at these crossing points. To confirm this prediction, molecular dynamical simulations of 2D Yukawa systems of κ = 0.75 for the conditions around the crossing point are performed. In the postshock region, the calculated various diagnostics of static structural measures, like the Voronoi diagram, the defect ratio, the probability distribution of the shape factors ξ, the pair correlation function g(r), and the static structure factor S(q), suggest that, for our studied system, the shock-induced melting happens when the compressional speed of the boundary is 0.212 a 0 ω p d < v left < 0.283 a 0 ω p d, the same as the prediction from the crossing point. read less USED (low confidence) B. Yao et al., “Cooperative roles of stacking fault energies on dislocation nucleation at bimetal interface through tunable potentials,” Computational Materials Science. 2021. link Times cited: 5 USED (low confidence) A. Khmich, A. Hassani, K. Sbiaai, and A. Hasnaoui, “Tuning of mechanical properties of Tantalum-based metallic glasses,” International Journal of Mechanical Sciences. 2021. link Times cited: 12 USED (low confidence) Y. Yang et al., “332 twinning transfer behavior and its effect on the twin shape in a beta-type Ti-23.1Nb-2.0Zr-1.0O alloy,” Journal of Materials Science & Technology. 2021. link Times cited: 5 USED (low confidence) D. F. Rojas, O. K. Orhan, and M. Ponga, “Dynamic recrystallization of Silver nanocubes during high-velocity impacts,” Acta Materialia. 2021. link Times cited: 10 USED (low confidence) J. Chen, D. Luscher, and S. Fensin, “The Modified Void Nucleation and Growth Model (MNAG) for Damage Evolution in BCC Ta,” Applied Sciences. 2021. link Times cited: 7 Abstract: A void coalescence term was proposed as an addition to the o… read moreAbstract: A void coalescence term was proposed as an addition to the original void nucleation and growth (NAG) model to accurately describe void evolution under dynamic loading. The new model, termed as modified void nucleation and growth model (MNAG model), incorporated analytic equations to explicitly account for the evolution of the void number density and the void volume fraction (damage) during void nucleation, growth, as well as the coalescence stage. The parameters in the MNAG model were fitted to molecular dynamics (MD) shock data for single-crystal and nanocrystalline Ta, and the corresponding nucleation, growth, and coalescence rates were extracted. The results suggested that void nucleation, growth, and coalescence rates were dependent on the orientation as well as grain size. Compared to other models, such as NAG, Cocks–Ashby, Tepla, and Tonks, which were only able to reproduce early or later stage damage evolution, the MNAG model was able to reproduce all stages associated with nucleation, growth, and coalescence. The MNAG model could provide the basis for hydrodynamic simulations to improve the fidelity of the damage nucleation and evolution in 3-D microstructures. read less USED (low confidence) Y. Yuan et al., “Revealing 3D atomic packing in liquid-like solids.” 2021. link Times cited: 0 Abstract:
Liquids and solids are two fundamental states of matter. H… read moreAbstract:
Liquids and solids are two fundamental states of matter. However, due to the lack of direct experimental determination, our understanding of the 3D atomic structure of liquids and amorphous solids remained speculative. Here we advance atomic electron tomography to determine for the first time the 3D atomic positions in monatomic amorphous materials, including a Ta thin film and two Pd nanoparticles. We observe that pentagonal bipyramids are the most abundant atomic motifs in these amorphous materials. Instead of forming icosahedra, the majority of pentagonal bipyramids arrange into a novel medium-range order, named the pentagonal bipyramid network. Molecular dynamic simulations further reveal that pentagonal bipyramid networks are prevalent in monatomic amorphous liquids, which rapidly grow in size and form icosahedra during the quench from the liquid state to glass state. The experimental method and results are expected to advance the study of the amorphous-crystalline phase transition and glass transition at the single-atom level. read less USED (low confidence) R. Kositski and D. Mordehai, “Employing molecular dynamics to shed light on the microstructural origins of the Taylor-Quinney coefficient,” Acta Materialia. 2021. link Times cited: 19 USED (low confidence) C. Bronkhorst et al., “Local micro-mechanical stress conditions leading to pore nucleation during dynamic loading,” International Journal of Plasticity. 2021. link Times cited: 13 USED (low confidence) Y.-S. Lin, G. P. P. Pun, and Y. Mishin, “Development of a physically-informed neural network interatomic potential for tantalum,” Computational Materials Science. 2021. link Times cited: 9 USED (low confidence) D. F. Rojas, O. K. Orhan, and M. Ponga, “Dynamic Recrystallization of Silver Nanoparticles During High-Velocity Impacts,” Mechanical Engineering eJournal. 2020. link Times cited: 0 Abstract: We study high-velocity impacts of Silver (Ag) single crystal… read moreAbstract: We study high-velocity impacts of Silver (Ag) single crystals nanocubes, their dynamic recrystallization, and post-impact lattice structure using a combination of molecular dynamics and ab-initio simulations. Our study shows that, upon the impact, some preferential orientations have the potential to develop an intricate, architected microstructures with grains of different sizes. These selected orientations correspond to the cases where at least eight or more slip systems were simultaneously activated, leading to an avalanche dislocations. These dislocations interact and have the ability to produce severe plastic work, stimulating recrystallization in the particles. On the other hand, dynamic recrystallization was not observed for the orientations with asynchronously activated slip systems besides large shock-wave pressures, plastic deformations, and large dislocation densities. In addition, using thermalized ab-initio simulations, we found that the severe plastic deformation can trigger phase transformation of the initial face centered cubic lattice structure to the 4H hexagonal closed-packed phase, which is thermodynamically more stable than the 2H hexagonal closed-packed phase. These results are in good agreement with experimental works. Our systematic numerical experiments shed light into the factors that promote the dynamic recrystallization and provide a pathway to control the microstructure and atomic structure by orienting nanoparticles with respect to the impact direction. read less USED (low confidence) Z. Hao, Z. Lou, and Y. Fan, “Influence of anisotropy of nickel-based single crystal superalloy in atomic and close-to-atomic scale cutting,” Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology. 2020. link Times cited: 13 USED (low confidence) J. Chen and S. Fensin, “Associating damage nucleation and distribution with grain boundary characteristics in Ta,” Scripta Materialia. 2020. link Times cited: 13 USED (low confidence) Y. Mo et al., “Different structural transitions of rapidly supercooled tantalum melt under pressure.,” Physical chemistry chemical physics : PCCP. 2020. link Times cited: 4 Abstract: Molecular dynamics (MD) simulations have been performed to s… read moreAbstract: Molecular dynamics (MD) simulations have been performed to study the effects of pressure (P) on the crystallization of tantalum (Ta) under different pressures from [0, 100] GPa. The average potential energy of atoms in the system, the pair distribution function and largest standard cluster analysis (LSCA) have been employed to analyze the structure evolution. It was found that the solidified state at 100 K changes from the complex crystal (β-Ta) through the body-centered cubic (bcc) crystal (α-Ta) to the hexagonal close-packed (hcp) crystal with increasing pressure. At P ≤ 3 GPa, the favorable state is β-Ta, which is composed of Z12, Z14 and Z15 atoms, and crystallization starts at the same temperature of crystallization (Tc = 1897 K), while there is a stochastic relationship between the crystallinity and pressure. At P ∈ [3, 57.5] GPa, the melt is always crystallized into rather perfect α-Ta, and Tc is nearly linear to pressure. However, when P > 57.5 GPa, a quite perfect bcc crystal is first formed and then transforms to a hcp crystal via a solid-solid (bcc-hcp) phase transition. Moreover, if the new hcp atoms formed in the bcc stage are arranged in regular grains, the bcc-hcp transition would take a multiple-intermediate-state pathway else, a single-intermediate-state pathway is the possibilty. Additionaly, the parameter δs readily reflects the crystallinity of the β-Ta, and smaller the value of δs, higher is the crystallinity of the β-Ta. Finally, during the bcc-hcp transition under high pressure, the volume reduction is due to the rearrangement of atoms rather than the reduction in the atomic radius; a slight increase in the number of nearest neighboring pairs results in a significant increase of the system energy. read less USED (low confidence) X. Fan, D. Pan, and M. Li, “Rethinking Lindemann criterion: A molecular dynamics simulation of surface mediated melting,” Acta Materialia. 2020. link Times cited: 17 USED (low confidence) P. Wang, Y. Bu, J. Liu, Q. Li, H. Wang, and W. Yang, “Atomic deformation mechanism and interface toughening in metastable high entropy alloy,” Materials Today. 2020. link Times cited: 41 USED (low confidence) J. Byggmastar, K. Nordlund, and F. Djurabekova, “Gaussian approximation potentials for body-centered-cubic transition metals,” Physical Review Materials. 2020. link Times cited: 22 Abstract: We develop a set of machine-learning interatomic potentials … read moreAbstract: We develop a set of machine-learning interatomic potentials for elemental V, Nb, Mo, Ta, and W using the Gaussian approximation potential framework. The potentials show good accuracy and transferability for elastic, thermal, liquid, defect, and surface properties. All potentials are augmented with accurate repulsive potentials, making them applicable to radiation damage simulations involving high-energy collisions. We study melting and liquid properties in detail and use the potentials to provide melting curves up to 400 GPa for all five elements. read less USED (low confidence) A. R. Hinkle et al., “Low friction in bcc metals via grain boundary sliding,” Physical Review Materials. 2020. link Times cited: 11 Abstract: Low friction is demonstrated with pure polycrystalline tanta… read moreAbstract: Low friction is demonstrated with pure polycrystalline tantalum sliding contacts in both molecular dynamics simulations and ultrahigh vacuum experiments. This phenomenon is shown to be correlated with deformation occurring primarily through grain boundary sliding and can be explained using a recently developed predictive model for the shear strength of metals. Specifically, low friction is associated with grain sizes at the interface being smaller than a critical, material-dependent value, where a crossover from dislocation mediated plasticity to grain-boundary sliding occurs. Low friction is therefore associated with inverse Hall-Petch behavior and softening of the interface. Direct quantitative comparisons between experiments and atomistic calculations are used to illustrate the accuracy of the predictions. read less USED (low confidence) G. Agarwal, R. Valisetty, and A. Dongare, “Shock wave compression behavior and dislocation density evolution in Al microstructures at the atomic scales and the mesoscales,” International Journal of Plasticity. 2020. link Times cited: 33 USED (low confidence) A. Khmich, K. Sbiaai, and A. Hasnaoui, “Annealing effect on elastic and structural behavior of Tantalum monatomic metallic glass,” Materials Chemistry and Physics. 2020. link Times cited: 8 USED (low confidence) N. Amadou, T. D. Rességuier, A. Dragon, and E. Brambrink, “Effects of orientation, lattice defects and temperature on plasticity and phase transition in ramp-compressed single crystal iron,” Computational Materials Science. 2020. link Times cited: 17 USED (low confidence) B. Yao and R. F. Zhang, “AADIS: An atomistic analyzer for dislocation character and distribution,” Comput. Phys. Commun. 2020. link Times cited: 19 USED (low confidence) S. Wang, H. Pan, A. He, P. Wang, and F.-guo Zhang, “Amorphous structure in single-crystal magnesium under compression along the
c
axis with ultrahigh strain rate,” Physical Review B. 2019. link Times cited: 3 USED (low confidence) E. Fransson and P. Erhart, “Defects from phonons: Atomic transport by concerted motion in simple crystalline metals,” Acta Materialia. 2019. link Times cited: 11 USED (low confidence) Y. Sato, S. Shinzato, T. Ohmura, and S. Ogata, “Atomistic prediction of the temperature- and loading-rate-dependent first pop-in load in nanoindentation,” International Journal of Plasticity. 2019. link Times cited: 32 USED (low confidence) X. Peng, N. Mathew, I. Beyerlein, K. Dayal, and A. Hunter, “A 3D phase field dislocation dynamics model for body-centered cubic crystals,” Computational Materials Science. 2019. link Times cited: 27 USED (low confidence) H. Sun, A. Kumar, and C. V. Singh, “Deformation behavior of BCC tantalum nanolayered composites with modulated layer thicknesses,” Materials Science and Engineering: A. 2019. link Times cited: 6 USED (low confidence) X. Wang, K. Li, Y. Zhu, W. Li, and W. Wang, “Molecular Dynamics Study on Mechanical Properties of Nanocrystalline tantalum,” 2019 IEEE 19th International Conference on Nanotechnology (IEEE-NANO). 2019. link Times cited: 1 Abstract: The study of nanocrystalline(NC) polycrystals is a hot topic… read moreAbstract: The study of nanocrystalline(NC) polycrystals is a hot topic, and the study of nanomaterial properties by molecular dynamics has become the first choice for many researchers. The purpose of this paper is to simulate the tensile tests of single and polycrystalline tantalum by molecular dynamics(MD) to obtain its mechanical properties. Firstly, the Ravelo-EAM potential was used to conduct tensile tests on tantalum in the <100> direction. Secondly, it can be seen that the elastic modulus E100 decreases with the temperature gradually increases from 1 K to 1500 K according to the simulation results. Finally, the Hall-Petch(H-P) effect based on grain size is verified from the tensile test of polycrystalline tantalum. read less USED (low confidence) Y. Chen et al., “Development of the interatomic potentials for W-Ta system,” Computational Materials Science. 2019. link Times cited: 22 USED (low confidence) A. Khmich, K. Sbiaai, and A. Hasnaoui, “Structural behavior of Tantalum monatomic metallic glass,” Journal of Non-Crystalline Solids. 2019. link Times cited: 24 USED (low confidence) W. Li, E. Hahn, X. Yao, T. Germann, and X. Zhang, “Shock induced damage and fracture in SiC at elevated temperature and high strain rate,” Acta Materialia. 2019. link Times cited: 42 USED (low confidence) H. Liu, Z. Chen, J. Mo, M. Wang, Y. Zhang, and W. Yang, “Brittle-to-ductile transition in monatomic Tantalum nanoporous metallic glass,” Journal of Non-Crystalline Solids. 2019. link Times cited: 18 USED (low confidence) Y. L. Li, J. Cai, and D. Mo, “Molecular dynamics simulations on the effect of nanovoid on shock-induced phase transition in uranium nitride,” Physics Letters A. 2019. link Times cited: 8 USED (low confidence) J. Wang, C. Chang, K. Song, L. Wang, and Y. Pan, “Short-range ordering in metallic supercooled liquids and glasses,” Journal of Alloys and Compounds. 2019. link Times cited: 11 USED (low confidence) C. Huang, X. Peng, Y. Zhao, S. Weng, B. Yang, and T. Fu, “Flow strength limit of nanocrystalline tantalum predicted with molecular dynamics simulations,” Materials Science and Engineering: A. 2018. link Times cited: 12 USED (low confidence) M. Tang, D. Fan, L. Wang, and S. Luo, “Deformation of metals under dynamic loading: Characterization via atomic-scale orientation mapping,” Computational Materials Science. 2018. link Times cited: 11 USED (low confidence) E. Hahn, S. Fensin, T. Germann, and G. Gray, “Orientation dependent spall strength of tantalum single crystals,” Acta Materialia. 2018. link Times cited: 54 USED (low confidence) J. Harrison, J. Schall, S. Maskey, P. Mikulski, M. T. Knippenberg, and B. Morrow, “Review of force fields and intermolecular potentials used in atomistic computational materials research,” Applied Physics Reviews. 2018. link Times cited: 99 Abstract: Molecular simulation is a powerful computational tool for a … read moreAbstract: Molecular simulation is a powerful computational tool for a broad range of applications including the examination of materials properties and accelerating drug discovery. At the heart of molecular simulation is the analytic potential energy function. These functions span the range of complexity from very simple functions used to model generic phenomena to complex functions designed to model chemical reactions. The complexity of the mathematical function impacts the computational speed and is typically linked to the accuracy of the results obtained from simulations that utilize the function. One approach to improving accuracy is to simply add more parameters and additional complexity to the analytic function. This approach is typically used in non-reactive force fields where the functional form is not derived from quantum mechanical principles. The form of other types of potentials, such as the bond-order potentials, is based on quantum mechanics and has led to varying levels of accuracy and transferability. When selecting a potential energy function for use in molecular simulations, the accuracy, transferability, and computational speed must all be considered. In this focused review, some of the more commonly used potential energy functions for molecular simulations are reviewed with an eye toward presenting their general forms, strengths, and weaknesses.Molecular simulation is a powerful computational tool for a broad range of applications including the examination of materials properties and accelerating drug discovery. At the heart of molecular simulation is the analytic potential energy function. These functions span the range of complexity from very simple functions used to model generic phenomena to complex functions designed to model chemical reactions. The complexity of the mathematical function impacts the computational speed and is typically linked to the accuracy of the results obtained from simulations that utilize the function. One approach to improving accuracy is to simply add more parameters and additional complexity to the analytic function. This approach is typically used in non-reactive force fields where the functional form is not derived from quantum mechanical principles. The form of other types of potentials, such as the bond-order potentials, is based on quantum mechanics and has led to varying levels of accuracy and transferabilit... read less USED (low confidence) M. Yang, J. Li, and B. Liu, “Fractal analysis on the cluster network in metallic liquid and glass,” Journal of Alloys and Compounds. 2018. link Times cited: 9 USED (low confidence) N. Amadou, T. D. Rességuier, A. Dragon, and E. Brambrink, “Coupling between plasticity and phase transition in shock- and ramp-compressed single-crystal iron,” Physical Review B. 2018. link Times cited: 27 Abstract: Molecular dynamics simulations have been used to investigate… read moreAbstract: Molecular dynamics simulations have been used to investigate the coupling process between plasticity and structural phase transformation in single-crystal iron under both shock and ramp compressions. In both cases, iron was found to yield via twinning. Then, the onset of the bcc-hcp phase transformation was shown to be tightly dependent on the plasticity history through a hardening-like effect, which in some conditions may inhibit the nucleation of the hcp phase. read less USED (low confidence) J. A. M. M. Abeywardhana, T. Germann, and R. Ravelo, “Strain rate dependence of deformation twinning in Ta.” 2018. link Times cited: 3 Abstract: Large-scale non-equilibrium molecular dynamics (NEMD) simula… read moreAbstract: Large-scale non-equilibrium molecular dynamics (NEMD) simulations are used to examine the role of dislocation density and strain rate on twin nucleation and deformation twinning in tantalum. The initial dislocation density was varied between 1011 − 1012 cm−2. The samples were compressed quasi-isentropically to pressures up to 100 GPa, at strain-rates in the 108 − 1012 s−1 range. The twin volume fraction, dislocation density and peak shear stress were evaluated as a function of strain and strain rate. Main results indicate that at these high strain rates, twinning in tantalum is strongly dependent on the dislocation density and strain (pressure). Deformation twinning, as measured by the twin volume fraction (TVF), increases with increase in strain rate for strain rates > 109 s−1. Below this value, a small fraction of twins nucleates but anneal out with time. Samples with lower fraction of twins equilibrate to defect states containing higher dislocation densities from those with initially higher twin volume fractions.Large-scale non-equilibrium molecular dynamics (NEMD) simulations are used to examine the role of dislocation density and strain rate on twin nucleation and deformation twinning in tantalum. The initial dislocation density was varied between 1011 − 1012 cm−2. The samples were compressed quasi-isentropically to pressures up to 100 GPa, at strain-rates in the 108 − 1012 s−1 range. The twin volume fraction, dislocation density and peak shear stress were evaluated as a function of strain and strain rate. Main results indicate that at these high strain rates, twinning in tantalum is strongly dependent on the dislocation density and strain (pressure). Deformation twinning, as measured by the twin volume fraction (TVF), increases with increase in strain rate for strain rates > 109 s−1. Below this value, a small fraction of twins nucleates but anneal out with time. Samples with lower fraction of twins equilibrate to defect states containing higher dislocation densities from those with initially higher twin volume... read less USED (low confidence) J. Hammerberg, R. Ravelo, and T. Germann, “Large-scale molecular dynamics studies of sliding friction in nanocrystalline aluminum.” 2018. link Times cited: 4 Abstract: We present the results of 138 million and 1.8 billion atom N… read moreAbstract: We present the results of 138 million and 1.8 billion atom Non-Equilibrium Molecular Dynamics (NEMD) simulations for Al-Al sliding friction at pressures of 15 GPa. Three-dimensional samples comprised of 4 nm, 20 nm and 50 nm grains were studied to times of 117 ns for the largest systems. We discuss the evolution of the initial grain size distribution to a steady state distribution that is statistically similar for all initial grain sizes. We compare the results for the frictional force to a rate dependent model that incorporates plasticity and discuss the relationships among grain size, grain morphology, dislocations and other defect structures, and plasticity.We present the results of 138 million and 1.8 billion atom Non-Equilibrium Molecular Dynamics (NEMD) simulations for Al-Al sliding friction at pressures of 15 GPa. Three-dimensional samples comprised of 4 nm, 20 nm and 50 nm grains were studied to times of 117 ns for the largest systems. We discuss the evolution of the initial grain size distribution to a steady state distribution that is statistically similar for all initial grain sizes. We compare the results for the frictional force to a rate dependent model that incorporates plasticity and discuss the relationships among grain size, grain morphology, dislocations and other defect structures, and plasticity. read less USED (low confidence) S. Fensin and E. Hahn, “Towards predicting susceptibility of grain boundaries to failure in BCC materials.” 2018. link Times cited: 5 Abstract: Several factors can affect the failure stress of a grain bou… read moreAbstract: Several factors can affect the failure stress of a grain boundary, such as grain boundary structure, energy and excess volume, in addition to its interactions with dislocations. In this paper, we focus on the influence of grain boundary energy and excess volume at the boundary on the failure stress of a grain boundary in tantalum from molecular-dynamics simulations. Flyer plate simulations were carried out for a handful of boundary types with different energies and excess volumes. These boundaries were chosen as model systems to represent various boundaries observed in “real” materials. For a small, but representative, set of boundaries explored, no direct correlation was observed between the void nucleation stress of a boundary and either its energy and excess volume. This result suggests that average properties of grain boundaries alone are not sufficient indicators of the failure strength of a boundary.Several factors can affect the failure stress of a grain boundary, such as grain boundary structure, energy and excess volume, in addition to its interactions with dislocations. In this paper, we focus on the influence of grain boundary energy and excess volume at the boundary on the failure stress of a grain boundary in tantalum from molecular-dynamics simulations. Flyer plate simulations were carried out for a handful of boundary types with different energies and excess volumes. These boundaries were chosen as model systems to represent various boundaries observed in “real” materials. For a small, but representative, set of boundaries explored, no direct correlation was observed between the void nucleation stress of a boundary and either its energy and excess volume. This result suggests that average properties of grain boundaries alone are not sufficient indicators of the failure strength of a boundary. read less USED (low confidence) E. Hahn, S. Fensin, and T. Germann, “The role of grain boundary orientation on void nucleation in tantalum.” 2018. link Times cited: 6 Abstract: It is generally understood that microstructure plays a signi… read moreAbstract: It is generally understood that microstructure plays a significant role in determining the deformation response of materials. During shock compression, grain boundaries serve as dislocation nucleation/pile-up/adsorption sites and grain size can alter the width of the shock front. During tensile release, grain boundaries are often “weak links” where spallation occurs. As such, a current deficit in predictive modeling capability is a quantitative description of these locations and their relative ability to serve as void nucleation sites - a challenging component of such a description is that spallation is inherently stochastic in nature. The inclination of the grain boundary plane with respect to the loading direction is thought to be a critical constituent in the resultant stress and failure at the boundary. Non-equilibrium molecular dynamics simulations are used to statistically quantify the influence of grain boundary inclination on the location of void nucleation and to highlight the emergence of stress hotspots at such boundaries. Boundaries oriented perpendicular to the loading direction are more likely to fail, but grain boundary inclination alone is not a complete predictor – i.e. not all perpendicular boundaries fail during spallation.It is generally understood that microstructure plays a significant role in determining the deformation response of materials. During shock compression, grain boundaries serve as dislocation nucleation/pile-up/adsorption sites and grain size can alter the width of the shock front. During tensile release, grain boundaries are often “weak links” where spallation occurs. As such, a current deficit in predictive modeling capability is a quantitative description of these locations and their relative ability to serve as void nucleation sites - a challenging component of such a description is that spallation is inherently stochastic in nature. The inclination of the grain boundary plane with respect to the loading direction is thought to be a critical constituent in the resultant stress and failure at the boundary. Non-equilibrium molecular dynamics simulations are used to statistically quantify the influence of grain boundary inclination on the location of void nucleation and to highlight the emergence of stress... read less USED (low confidence) M. Yaghoobi and G. Voyiadjis, “The effects of temperature and strain rate in fcc and bcc metals during extreme deformation rates,” Acta Materialia. 2018. link Times cited: 43 USED (low confidence) J. Feng, P. Chen, and M. Li, “Absence of 2.5 power law for fractal packing in metallic glasses,” Journal of Physics: Condensed Matter. 2018. link Times cited: 3 Abstract: Atomic packing is still a mystery for topologically disorder… read moreAbstract: Atomic packing is still a mystery for topologically disordered amorphous solids owing primarily to the absence of Bragg diffraction in this class of materials. Among many hypotheses, fractal packing is suggested based on a scaling relation with ‘2.5 power law’ found in multicomponent metallic glasses. Here we examine the atomic packing critically in a pure Tantalum metallic glass under hydrostatic pressure. Without complications of chemical compositions as in the multicomponent systems, the genuine amorphous structure along in the single component metallic glass exhibits a cubic scaling exponent that indicates absence of the 2.5 power law. However, fractal-like short- and medium-range icosahedral cluster packing is observed; but these substructures do not contribute to the fractal dimension through the power law scaling. read less USED (low confidence) A. P. Moore, J. Brown, H. Lim, and J. Lane, “Verification of experimental dynamic strength methods with atomistic ramp-release simulations,” Physical Review Materials. 2018. link Times cited: 4 USED (low confidence) M. Tang, Y. Y. Zhang, J. E, and S. Luo, “Simulations of X-ray diffraction of shock-compressed single-crystal tantalum with synchrotron undulator sources.,” Journal of synchrotron radiation. 2018. link Times cited: 5 Abstract: Polychromatic synchrotron undulator X-ray sources are useful… read moreAbstract: Polychromatic synchrotron undulator X-ray sources are useful for ultrafast single-crystal diffraction under shock compression. Here, simulations of X-ray diffraction of shock-compressed single-crystal tantalum with realistic undulator sources are reported, based on large-scale molecular dynamics simulations. Purely elastic deformation, elastic-plastic two-wave structure, and severe plastic deformation under different impact velocities are explored, as well as an edge release case. Transmission-mode diffraction simulations consider crystallographic orientation, loading direction, incident beam direction, X-ray spectrum bandwidth and realistic detector size. Diffraction patterns and reciprocal space nodes are obtained from atomic configurations for different loading (elastic and plastic) and detection conditions, and interpretation of the diffraction patterns is discussed. read less USED (low confidence) M. Cheng, C. Li, M. Tang, L. Lu, Z. Li, and S. Luo, “Intragranular void formation in shock-spalled tantalum: Mechanisms and governing factors,” Acta Materialia. 2018. link Times cited: 46 USED (low confidence) T. C. O’Connor, R. Elder, Y. R. Sliozberg, T. Sirk, J. Andzelm, and M. Robbins, “Molecular origins of anisotropic shock propagation in crystalline and amorphous polyethylene,” Physical Review Materials. 2018. link Times cited: 16 USED (low confidence) B. Pang et al., “The defect evolution in shock loaded tantalum single crystals,” Acta Materialia. 2017. link Times cited: 27 USED (low confidence) C. Wehrenberg et al., “In situ X-ray diffraction measurement of shock-wave-driven twinning and lattice dynamics,” Nature. 2017. link Times cited: 104 USED (low confidence) C. Ruestes, E. Bringa, Y. Gao, and H. Urbassek, “Molecular Dynamics Modeling of Nanoindentation.” 2017. link Times cited: 35 USED (low confidence) A. Neogi and N. Mitra, “A metastable phase of shocked bulk single crystal copper: an atomistic simulation study,” Scientific Reports. 2017. link Times cited: 43 USED (low confidence) C. Huang et al., “Molecular dynamics simulation of BCC Ta with coherent twin boundaries under nanoindentation,” Materials Science and Engineering A-structural Materials Properties Microstructure and Processing. 2017. link Times cited: 56 USED (low confidence) A. Hermann, “Chemical Bonding at High Pressure.” 2017. link Times cited: 4 USED (low confidence) G. Agarwal and A. Dongare, “Atomistic study of shock Hugoniot of single crystal Mg.” 2017. link Times cited: 10 Abstract: Molecular Dynamics (MD) simulations are carried out to inves… read moreAbstract: Molecular Dynamics (MD) simulations are carried out to investigate the shock Hugoniot for single crystal Mg using a planar shock. The MD simulations were carried out using two embedded atom method (EAM) potentials for impact velocities in the range of 500 m/s – 2000 m/s. The anisotropic behavior of shock wave propagation with loading orientation of the crystal is investigated by computing the particle velocity profiles for impact along [0001], [112¯0] and [101¯0] orientations. A split two wave (elastic-plastic) structure above the Hugoniot elastic limit is observed for all the three orientations considered. The shock pressure and the shock velocity of the elastic and the plastic wave are computed as functions of impact velocity. The Hugoniot response predicted for both the potentials agrees very well with the experimental data and therefore suggests that these can be reliably used to model the shock response of single crystal Mg. read less USED (low confidence) D. Tramontina, E. Hahn, M. Meyers, and E. Bringa, “Simulation of tantalum nanocrystals under shock-wave loading: Dislocations and twinning.” 2017. link Times cited: 17 Abstract: We simulate strong shock waves in nanocrystalline tantalum u… read moreAbstract: We simulate strong shock waves in nanocrystalline tantalum using atomistic molecular dynamics simulations, for particle velocities in the range 0.35-2.0 km s−1, which induce pressures in the range 20-195 GPa. Our simulations explore strain rates in the range 108 s−1 - 1010 s−1, and lead to a peak strength in the range 3-15 GPa. Nanocrystalline tantalum exposed to strong shock waves demonstrates deformation enabled by concomitant dislocations, twinning, and grain boundary activity at a variety of particle velocities. Twinning is observed for a mean grain size of 7 nm, starting at around 32 GPa, in disagreement with models which predict a Hall-Petch behavior for twinning, i.e. a twinning stress scaling with grain size d as d−0.5, and supporting the presence of an inverse Hall-Petch effect for twinning at small grain sizes. read less USED (low confidence) E. Hahn, T. Germann, R. Ravelo, J. Hammerberg, and M. Meyers, “Non-equilibrium molecular dynamics simulations of spall in single crystal tantalum.” 2017. link Times cited: 11 Abstract: Ductile tensile failure of tantalum is examined through larg… read moreAbstract: Ductile tensile failure of tantalum is examined through large scale non-equilibrium molecular dynamics simulations. Several loading schemes including flyer plate impact, decaying shock loading via a frozen piston, and quasi-isentropic (constant strain-rate) expansion are employed to span tensile strain-rates of 108 to 1014 per second. Single crystals of 〈001〉 orientation are specifically evaluated to eliminate grain boundary effects. Heterogeneous void nucleation occurs principally at the intersection of deformation twins in single crystals. At high strain rates, multiple spall events occur throughout the material and voids continue to nucleate until relaxation waves arrive from adjacent events. At ultra-high strain rates, those approaching or exceeding the atomic vibrational frequency, spall strength saturates near the maximum theoretical spall strength. read less USED (low confidence) C. Liu, C. Xu, Y. Cheng, X.-R. Chen, and L. Cai, “Orientation-dependent responses of tungsten single crystal under shock compression via molecular dynamics simulations,” Computational Materials Science. 2015. link Times cited: 15 USED (low confidence) C.-H. Lu, E. Hahn, B. Remington, B. Maddox, E. Bringa, and M. A. Meyers, “Phase Transformation in Tantalum under Extreme Laser Deformation,” Scientific Reports. 2015. link Times cited: 32 USED (low confidence) K. Zhang, M. Fan, Y. Liu, J. Schroers, M. Shattuck, and C. O’Hern, “Beyond packing of hard spheres: The effects of core softness, non-additivity, intermediate-range repulsion, and many-body interactions on the glass-forming ability of bulk metallic glasses.,” The Journal of chemical physics. 2015. link Times cited: 16 Abstract: When a liquid is cooled well below its melting temperature a… read moreAbstract: When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate Rc, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. Rc (or the corresponding critical casting thickness dc) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small Rc < 10(-2) K/s, pure metals and most alloys are typically poor glass-formers with large Rc > 10(10) K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with Rc approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for designing BMGs with cm or greater casting thickness. read less USED (low confidence) E. S. Wise, M. Liu, and T. Miller, “Sputtering of cubic metal crystals by low-energy xenon-ions,” Computational Materials Science. 2015. link Times cited: 5 USED (low confidence) J. Hammerberg, R. Ravelo, T. Germann, and J. Milhans, “Grain dynamics in compressed polycrystalline Al interfaces sliding at high velocities,” Bulletin of the American Physical Society. 2015. link Times cited: 3 Abstract: We discuss the relationship between grain structure and the … read moreAbstract: We discuss the relationship between grain structure and the frictional force for polycrystalline Al interfaces with grain sizes of 13, 20 and 50 nm as seen in large scale NonEquilibrium Molecular Dynamics (NEMD) simulations at nominal pressures of 15 GPa. Simulation sizes were 138 M (Million) atoms for the 13 and 20 nm grain size samples and 1.8 B (Billion) atoms for the 50 nm samples with times to 40 ns. We find that the frictional force in the steady state is independent of the initial grain size and that the grain distribution evolves to a dynamical steady state characterized by a sequence of grain growth and refinement events at very large local plastic strains and strain rates. Based upon these simulations, a meso/macro-scale model has been developed that reproduces the NEMD results for over two orders of magnitude in sliding velocity encompassing both solid and fluid regimes. read less USED (low confidence) Y. Gao, C. Ruestes, D. Tramontina, and H. Urbassek, “Comparative simulation study of the structure of the plastic zone produced by nanoindentation,” Journal of The Mechanics and Physics of Solids. 2015. link Times cited: 111 USED (low confidence) D. McGonegle, D. Milathianaki, B. Remington, J. Wark, and A. Higginbotham, “Simulations of in situ x-ray diffraction from uniaxially compressed highly textured polycrystalline targets,” Journal of Applied Physics. 2015. link Times cited: 18 Abstract: A growing number of shock compression experiments, especiall… read moreAbstract: A growing number of shock compression experiments, especially those involving laser compression, are taking advantage of in situ x-ray diffraction as a tool to interrogate structure and microstructure evolution. Although these experiments are becoming increasingly sophisticated, there has been little work on exploiting the textured nature of polycrystalline targets to gain information on sample response. Here, we describe how to generate simulated x-ray diffraction patterns from materials with an arbitrary texture function subject to a general deformation gradient. We will present simulations of Debye-Scherrer x-ray diffraction from highly textured polycrystalline targets that have been subjected to uniaxial compression, as may occur under planar shock conditions. In particular, we study samples with a fibre texture, and find that the azimuthal dependence of the diffraction patterns contains information that, in principle, affords discrimination between a number of similar shock-deformation mechanisms. For certain cases, we compare our method with results obtained by taking the Fourier transform of the atomic positions calculated by classical molecular dynamics simulations. Illustrative results are presented for the shock-induced α–ϵ phase transition in iron, the α–ω transition in titanium and deformation due to twinning in tantalum that is initially preferentially textured along [001] and [011]. The simulations are relevant to experiments that can now be performed using 4th generation light sources, where single-shot x-ray diffraction patterns from crystals compressed via laser-ablation can be obtained on timescales shorter than a phonon period. read less USED (low confidence) K. Wang, S. Xiao, H. Deng, W. Zhu, and W. Hu, “An atomic study on the shock-induced plasticity and phase transition for iron-based single crystals,” International Journal of Plasticity. 2014. link Times cited: 90 USED (low confidence) D. Tramontina, C. Ruestes, Y. Tang, and E. Bringa, “Orientation-dependent response of defective Tantalum single crystals,” Computational Materials Science. 2014. link Times cited: 14 USED (low confidence) D. Tramontina et al., “Molecular dynamics simulations of shock-induced plasticity in tantalum,” High Energy Density Physics. 2014. link Times cited: 71 USED (low confidence) A. Higginbotham and D. McGonegle, “Prediction of Debye-Scherrer diffraction patterns in arbitrarily strained samples,” Journal of Applied Physics. 2013. link Times cited: 17 Abstract: The prediction of Debye-Scherrer diffraction patterns from s… read moreAbstract: The prediction of Debye-Scherrer diffraction patterns from strained samples is typically conducted in the small strain limit. Although valid for small deviations from the hydrostat (such as the conditions of finite strength typically observed in diamond anvil cells) this assertion is likely to fail for the large strain anisotropies (often of order 10% in normal strain) found in uniaxially loaded dynamic compression experiments. In this paper, we derive a general form for the (θB,ϕ) dependence of the diffraction for an arbitrarily deformed polycrystalline sample in any geometry, and of any crystal symmetry. We show that this formula is consistent with ray traced diffraction for highly strained computationally generated polycrystals, and that the formula shows deviations from the widely used small strain solutions previously reported. read less USED (low confidence) Y. Zhang, Z. Xiao, and X. Bai, “Effect of Cr Concentration on ½<111> to <100> Dislocation Loop Transformation in Fe-Cr alloys,” Journal of Nuclear Materials. 2021. link Times cited: 10 USED (low confidence) N. Amadou, T. D. Rességuier, and A. Dragon, “Coupling between plasticity and phase transition in single crystal iron at ultra-high strain rate.” 2020. link Times cited: 2 USED (low confidence) E. Rothchild, Q. J. Li, and E. Ma, “On the validity of using the Debye model to quantitatively correlate the shear modulus with vibrational properties in cubic metals,” Scripta Materialia. 2019. link Times cited: 1 USED (low confidence) J. Lane, “Shock Compression of Porous Materials and Foams Using Classical Molecular Dynamics,” Shock Wave and High Pressure Phenomena. 2019. link Times cited: 0 USED (low confidence) J. R. Murillo, R. Mohan, and A. Mohamed, “Constitutive Material Models for High Strain Rate Behavior of Cementitious Materials from Material Chemistry—Molecular Dynamics Modeling Methodology with Illustrative Application to Hydrated Calcium Silicate Hydrate Jennite.” 2018. link Times cited: 2 USED (low confidence) A. P. Moore, H. Lim, J. Brown, and J. Lane, “Molecular scale study of the plastic response of tantalum under ramp compression and release.” 2018. link Times cited: 0 USED (low confidence) Z. R. Liu and R. Zhang, “AACSD: An atomistic analyzer for crystal structure and defects,” Comput. Phys. Commun. 2018. link Times cited: 19 USED (low confidence) L. Hai, H. Jie, Z. Zhi-xuan, and M. Zhao-xia, “Atomistic Simulations of Elastic-Plastic Deformation in Nickel Single Crystal under Shock Loading,” Procedia Engineering. 2017. link Times cited: 3 USED (low confidence) G. Norman et al., “What for and which exaflops supercomputers are necessary in natural sciences.” 2015. link Times cited: 3 NOT USED (high confidence) Y. Zhang, N. Chen, C. Bronkhorst, H. Cho, and R. Argus, “Data-driven statistical reduced-order modeling and quantification of polycrystal mechanics leading to porosity-based ductile damage,” Journal of the Mechanics and Physics of Solids. 2023. link Times cited: 0 NOT USED (high confidence) B. Hamilton, M. Kroonblawd, J. Macatangay, H. Springer, and A. Strachan, “Intergranular Hotspots: A Molecular Dynamics Study on the Influence of Compressive and Shear Work,” The Journal of Physical Chemistry C. 2023. link Times cited: 3 Abstract: Numerous crystal- and microstructural-level mechanisms are a… read moreAbstract: Numerous crystal- and microstructural-level mechanisms are at play in the formation of hotspots, which are known to govern high explosive initiation behavior. Most of these mechanisms, including pore collapse, interfacial friction, and shear banding, involve both compressive and shear work done within the material and have thus far remained difficult to separate. We assess hotspots formed at shocked crystal-crystal interfaces using quasi-1D molecular dynamics simulations that isolate effects due to compression and shear. Two high explosive materials are considered (TATB and PETN) that exhibit distinctly different levels of molecular conformational flexibility and crystal packing anisotropy. Temperature and intra-molecular strain energy localization in the hotspot is assessed through parametric variation of the crystal orientation and two velocity components that respectively modulate compression and shear work. The resulting hotspots are found to be highly localized to a region within 5-20 nm of the crystal-crystal interface. Compressive work plays a considerably larger role in localizing temperature and intra-molecular strain energy for both materials and all crystal orientations considered. Shear induces a moderate increase in energy localization relative to unsheared cases only for relatively weak compressive shock pressures of approximately 10 GPa. These results help isolate and rank the relative importance of hotspot generation mechanisms and are anticipated to guide the treatment of crystal-crystal interfaces in coarse-grained models of polycrystalline high explosive materials. read less NOT USED (high confidence) B. Hamilton, M. Kroonblawd, and A. Strachan, “Extemporaneous Mechanochemistry: Shock-Wave-Induced Ultrafast Chemical Reactions Due to Intramolecular Strain Energy.,” The journal of physical chemistry letters. 2022. link Times cited: 12 Abstract: Regions of energy localization referred to as hotspots are k… read moreAbstract: Regions of energy localization referred to as hotspots are known to govern shock initiation and the run-to-detonation in energetic materials. Mounting computational evidence points to accelerated chemistry in hotspots from large intramolecular strains induced via the interactions between the shock wave and microstructure. However, definite evidence mapping intramolecular strain to accelerated or altered chemical reactions has so far been elusive. From a large-scale reactive molecular dynamics simulation of the energetic material 1,3,5-triamino-2,4,6-trinitrobenzene, we map decomposition kinetics to molecular temperature and intramolecular strain energy prior to reaction. Both temperature and intramolecular strain are shown to accelerate chemical kinetics. A detailed analysis of the atomistic trajectory shows that intramolecular strain can induce a mechanochemical alteration of decomposition mechanisms. The results in this paper could inform continuum-level chemistry models to account for a wide range of mechanochemical effects. read less NOT USED (high confidence) P. Heighway and J. Wark, “Slip competition and rotation suppression in tantalum and copper during dynamic uniaxial compression.” 2022. link Times cited: 1 Abstract: When compressed, a metallic specimen will generally experien… read moreAbstract: When compressed, a metallic specimen will generally experience changes to its crystallographic texture due to plasticity-induced rotation. Ultrafast x-ray diffraction techniques make it possible to measure rotation of this kind in targets dynamically compressed over nanosecond timescales to the kind of pressures ordinarily encountered in planetary interiors. The axis and the extent of the local rotation can provide hints as to the combination of plasticity mechanisms activated by the rapid uniaxial compression, thus providing valuable information about the underlying dislocation kinetics operative during extreme loading conditions. We present large-scale molecular dynamics simulations of shock-induced lattice rotation in three model crystals whose behavior has previously been characterized in dynamic-compression experiments: tantalum shocked along its [101] direction, and copper shocked along either [001] or [111]. We find that, in all three cases, the texture changes predicted by the simulations are consistent with those measured experimentally using in situ x-ray diffraction. We show that while tantalum loaded along [101] and copper loaded along [001] both show pronounced rotation due to asymmetric multiple slip, the orientation of copper shocked along [111] is predicted to be stabilized by opposing rotations arising from competing, symmetrically equivalent slip systems. read less NOT USED (high confidence) O. Karnbach, P. Heighway, D. McGonegle, R. Rudd, G. Gregori, and J. Wark, “Molecular dynamics simulations of inelastic x-ray scattering from shocked copper,” Journal of Applied Physics. 2021. link Times cited: 1 Abstract: By taking the spatial and temporal Fourier transforms of the… read moreAbstract: By taking the spatial and temporal Fourier transforms of the coordinates of the atoms in molecular dynamics simulations conducted using an embedded-atom-method potential, we calculate the inelastic scattering of x rays from copper single crystals shocked along [001] to pressures of up to 70 GPa. Above the Hugoniot elastic limit, we find that the copious stacking faults generated at the shock front introduce strong quasi-elastic scattering (QES) that competes with the inelastic scattering signal, which remains discernible within the first Brillouin zone; for specific directions in reciprocal space outside the first zone, the QES dominates the inelastic signal overwhelmingly. The synthetic scattering spectra we generate from our Fourier transforms suggest that energy resolutions of order 10 meV would be required to distinguish inelastic from quasi-elastic scattering within the first Brillouin zone of shock-loaded copper. We further note that high-resolution inelastic scattering also affords the possibility of directly measuring particle velocities via the Doppler shift. These simulations are of relevance to future planned inelastic scattering experiments at x-ray Free Electron Laser facilities. read less NOT USED (high confidence) P. Avraam et al., “Crystal plasticity finite element simulation of lattice rotation and x-ray diffraction during laser shock compression of tantalum,” Physical Review Materials. 2021. link Times cited: 2 Abstract: Wehrenberg et. al. [Nature 550 496 (2017)] used ultrafast in… read moreAbstract: Wehrenberg et. al. [Nature 550 496 (2017)] used ultrafast in situ x-ray diffraction at the LCLS x-ray free-electron laser facility to measure large lattice rotations resulting from slip and deformation twinning in shock-compressed laser-driven [110] fibre textured tantalum polycrystal. We employ a crystal plasticity finite element method model, with slip kinetics based closely on the isotropic dislocation-based Livermore Multiscale Model [Barton et. al., J. Appl. Phys. 109 (2011)], to analyse this experiment. We elucidate the link between the degree of lattice rotation and the kinetics of plasticity, demonstrating that a transition occurs at shock pressures of $\sim$27 GPa, between a regime of relatively slow kinetics, resulting in a balanced pattern of slip system activation and therefore relatively small net lattice rotation, and a regime of fast kinetics, due to the onset of nucleation, resulting in a lop-sided pattern of deformation-system activation and therefore large net lattice rotations. We demonstrate a good fit between this model and experimental x-ray diffraction data of lattice rotation, and show that this data is constraining of deformation kinetics. read less NOT USED (high confidence) A. Mishra, C. Kunka, M. J. Echeverría, R. Dingreville, and A. Dongare, “Fingerprinting shock-induced deformations via diffraction,” Scientific Reports. 2021. link Times cited: 9 NOT USED (high confidence) D.-S. Wu, Y. Zhu, L. Zhao, M. Huang, and Z. Li, “Atomistic investigation of mechanical response and deformation mechanism of BCC Ta under double shock loading,” Journal of Applied Physics. 2021. link Times cited: 7 Abstract: Engineering structures or materials are often subjected to m… read moreAbstract: Engineering structures or materials are often subjected to multiple shock loadings. Mechanical response and its physical mechanism under such loadings are extremely complex and need to be studied in depth. To reveal double shock-induced deformation and microstructural evolution in the key structural material Ta, large-scale non-equilibrium molecular dynamics simulations of monocrystalline and polycrystalline Ta under double shock loading were performed. The results show that the activation and re-evolution of twins and dislocations introduced by the first shock dominate the plastic deformation during the second one. Some crystallographic orientation dependent mechanisms of plastic deformation under the second shock are revealed. Twin-dislocation conversion is dominant in the ⟨100⟩-orientated monocrystalline and polycrystalline Ta, while dislocation slipping is dominant in the ⟨110⟩- and ⟨111⟩-orientated Ta. The dependence of flow strength on the loading-paths of single and double shocks was also investigated. Shock-induced amorphization and recrystallization are observed in the single shock-loaded Ta models, leading to lower flow strengths than those of the double shock-loaded ones. These results help understand the complex relationship between the dynamic strength and intrinsic deformation mechanism of Ta under multiple shock loadings. read less NOT USED (high confidence) K. Ma, J. Chen, and A. Dongare, “Role of pre-existing dislocations on the shock compression and spall behavior in single-crystal copper at atomic scales,” Journal of Applied Physics. 2021. link Times cited: 14 Abstract: Large-scale molecular dynamics simulations are carried out t… read moreAbstract: Large-scale molecular dynamics simulations are carried out to investigate the role of pre-existing dislocation loops on the shock-induced deformation and spall behavior of single-crystal Cu microstructures. This study investigates the role of loading orientation and initial density of pre-existing dislocations on the decay behavior of the Hugoniot elastic limit (HEL) as well as the damage nucleation and growth behavior during spall failure of single-crystal Cu systems. The results suggest that the presence of pre-existing dislocation loops results in a decrease of the shock wave velocity and a substantial decay of the HEL values. The increased decay behavior is attributed to the decrease in the density of Shockley partials at the shock front as the shock wave travels through the metal as compared to defect-free initial single-crystal microstructures. Similarly, the presence of pre-existing dislocations is observed to result in increased values for the spall strength as compared to defect-free initial single-crystal microstructures wherein a higher density of dislocations results in the nucleation of a larger number of smaller voids. The decay behavior of the HEL values is observed to have a power–law dependence on the shock propagation distance with the initial dislocation density as a parameter. Similarly, a power–law dependence is also proposed for the number of voids nucleated at the spall plane with a dependence on the size of the voids as well as the initial density of dislocations. The evolution of microstructure (dislocation densities and voids) for the various loading orientations and initial densities of dislocations is discussed. read less NOT USED (high confidence) B. Pang, I. Jones, J. Millett, G. Whiteman, and Y. Chiu, “The defect evolution in 1-D shocked tantalum single crystals,” Journal of Materials Science. 2021. link Times cited: 5 NOT USED (high confidence) P. Heighway and J. Wark, “Kinematics of slip-induced rotation for uniaxial shock or ramp compression,” Journal of Applied Physics. 2020. link Times cited: 5 Abstract: When a metallic specimen is plastically deformed, its underl… read moreAbstract: When a metallic specimen is plastically deformed, its underlying crystal structure must often rotate in order to comply with its macroscopic boundary conditions. There is growing interest within the dynamic compression community in exploiting x-ray diffraction measurements of lattice rotation to infer which combinations of plasticity mechanisms are operative in uniaxially shock- or ramp-compressed crystals, thus informing materials science at the greatest extremes of pressure and strain rate. However, it is not widely appreciated that several of the existing models linking rotation to slip activity are fundamentally inapplicable to a planar compression scenario. We present molecular dynamics simulations of single crystals suffering true uniaxial strain, and show that the Schmid and Taylor analyses used in traditional materials science fail to predict the ensuing lattice rotation. We propose a simple alternative framework based on the elastoplastic decomposition that successfully recovers the observed rotation for these single crystals, and can further be used to identify the operative slip systems and the amount of activity upon them in the idealized cases of single and double slip. read less NOT USED (high confidence) S. Galitskiy and A. Dongare, “Modeling the damage evolution and recompression behavior during laser shock loading of aluminum microstructures at the mesoscales,” Journal of Materials Science. 2020. link Times cited: 15 NOT USED (high confidence) M. Tang, J. W. Huang, J. E, Y. Y. Zhang, and S. Luo, “Full strain tensor measurements with X-ray diffraction and strain field mapping: a simulation study.,” Journal of synchrotron radiation. 2020. link Times cited: 2 Abstract: Strain tensor measurements are important for understanding e… read moreAbstract: Strain tensor measurements are important for understanding elastic and plastic deformation, but full bulk strain tensor measurement techniques are still lacking, in particular for dynamic loading. Here, such a methodology is reported, combining imaging-based strain field mapping and simultaneous X-ray diffraction for four typical loading modes: one-dimensional strain/stress compression/tension. Strain field mapping resolves two in-plane principal strains, and X-ray diffraction analysis yields volumetric strain, and thus the out-of-plane principal strain. This methodology is validated against direct molecular dynamics simulations on nanocrystalline tantalum. This methodology can be implemented with simultaneous X-ray diffraction and digital image correlation in synchrotron radiation or free-electron laser experiments. read less NOT USED (high confidence) K. V. Reddy, C. Deng, and S. Pal, “Intensification of shock damage through heterogeneous phase transition and dislocation loop formation due to presence of pre-existing line defects in single crystal Cu,” Journal of Applied Physics. 2019. link Times cited: 4 Abstract: In general, shock wave deformation studies of perfect single… read moreAbstract: In general, shock wave deformation studies of perfect single crystals may cause disagreement with the experimental findings as the complete elimination of all defects in the metallic system is not possible in reality. Here, we have studied the influence of edge and screw dislocations on the intensification of damage produced during the propagation of shock at various velocities. Various analyses have been performed such as common neighbor analysis, atomic strain analysis, stress analysis, and kinetic energy mapping to investigate the underlying plastic deformation mechanisms. Results have revealed that the presence of edge dislocations has caused intensified damage through localized amorphization and phase transition. In comparison with the perfect crystal, the presence of pre-existing edge dislocations has incurred an additional damage of ∼17% to the specimen region. On the other hand, the presence of screw dislocations in the specimen causes damage through shear bands and dislocation loop formation, which is found to constitute greater than 80% of the specimen region. read less NOT USED (high confidence) R. Kositski and D. Mordehai, “On the origin of the stress spike decay in the elastic precursor in shocked metals,” Journal of Applied Physics. 2019. link Times cited: 10 Abstract: High-strain rate experiments are commonly employed to study … read moreAbstract: High-strain rate experiments are commonly employed to study the dynamic strength of metals, by generating a plane shock wave and measuring the amplitude of the elastic precursor. In some cases, the shock wave is rapidly relaxed after the elastic precursor, leading to a spike in the stress wave. We propose that the observed spike and the following relaxation arise from the interplay between the rate by which dislocations are nucleated and the mobility of the existing ones. In addition, we suggest that the elastic precursor decays since glide takes a larger role in the plastic deformation as the plastic strain rate decreases. The interplay is demonstrated in a physically, dislocation-based dynamic strength model, using dislocation mobility rules from molecular dynamics simulations, as well as a dislocation nucleation model which is fitted using a metamodel optimization technique. Our results show that the stress spike and its decay in annealed body-centered cubic specimens arise from the need to nucleate dislocations to generate a plastic deformation when the mobility of existing dislocations is insufficient to accommodate plastic strain. Cold-rolled targets have sufficient amount of initial dislocations, so glide, rather than nucleation, can accommodate the plastic relaxation, and as such do not exhibit a spike. These insights shed light on the experimentally observed differences between dynamic and static strength of materials, and, in particular, on the anomalous dependence of the dynamic strength on temperature and pretreatment of materials at high-strain rates.High-strain rate experiments are commonly employed to study the dynamic strength of metals, by generating a plane shock wave and measuring the amplitude of the elastic precursor. In some cases, the shock wave is rapidly relaxed after the elastic precursor, leading to a spike in the stress wave. We propose that the observed spike and the following relaxation arise from the interplay between the rate by which dislocations are nucleated and the mobility of the existing ones. In addition, we suggest that the elastic precursor decays since glide takes a larger role in the plastic deformation as the plastic strain rate decreases. The interplay is demonstrated in a physically, dislocation-based dynamic strength model, using dislocation mobility rules from molecular dynamics simulations, as well as a dislocation nucleation model which is fitted using a metamodel optimization technique. Our results show that the stress spike and its decay in annealed body-centered cubic specimens arise from the need to nucleate di... read less NOT USED (high confidence) J. Byggmastar, A. Hamedani, K. Nordlund, and F. Djurabekova, “Machine-learning interatomic potential for radiation damage and defects in tungsten,” Physical Review B. 2019. link Times cited: 58 Abstract: We introduce a machine-learning interatomic potential for tu… read moreAbstract: We introduce a machine-learning interatomic potential for tungsten using the Gaussian Approximation Potential framework. We specifically focus on properties relevant for simulations of radiation-induced collision cascades and the damage they produce, including a realistic repulsive potential for the short-range many-body cascade dynamics and a good description of the liquid phase. Furthermore, the potential accurately reproduces surface properties and the energetics of vacancy and self-interstitial clusters, which have been long-standing deficiencies of existing potentials. The potential enables molecular dynamics simulations of radiation damage in tungsten with unprecedented accuracy. read less NOT USED (high confidence) B. Huang, G. Li, X.-qiu Yang, and P. Zhai, “Capturing anharmonic and anisotropic natures in the thermotics and mechanics of Bi2Te3 thermoelectric material through an accurate and efficient potential,” Journal of Physics D: Applied Physics. 2019. link Times cited: 9 Abstract: Force-field-(FF)-based molecular simulation is essential but… read moreAbstract: Force-field-(FF)-based molecular simulation is essential but challenging in the theoretical research of complex thermoelectric (TE) materials. As they are general and crucial in TE semiconductors, the structural natures of anharmonicity and anisotropy can help us understand the inherent relation between thermal and mechanical behavior, and therefore the reliability of FF studies can be assessed. In this paper, given prior knowledge of the structural, mechanical and thermal properties as well as the limitations and necessary approximations of the FF method, a feasible and detailed FF modeling scheme and simulation has been designed for Bi2Te3, which is a typical high-performance TE material. Using the complementary approach combining quasi-harmonic lattice and molecular dynamics, the obtained potential is systematically confirmed to be accurate and efficient for the prediction of anharmonic and anisotropic behavior in thermotics and mechanics over a wide temperature range compared with the present Bi2Te3 models. This reveals that the intrinsic anisotropy and anharmonicity can measure the asymmetry of crystal lattices and the interatomic force in the current state. In addition, the significant distinction of temperature-dependent anharmonic effects in different directions of Bi2Te3 stems from its layered hierarchical structure, in which weak van der Waals bonding will probably be the key structural factor in comprehensively improving performance for mass production and wearable application. This prior-knowledge-based FF study is also suggested as a bridge between the theoretical understanding of micro-mechanisms and the experimental measurement of TE material properties, leading to a general framework of molecular simulation for other complex energy materials. read less NOT USED (high confidence) K. Wang, W. Zhu, M. Xiang, Y. Xu, G. Li, and J. Chen, “Improved embedded-atom model potentials of Pb at high pressure: application to investigations of plasticity and phase transition under extreme conditions,” Modelling and Simulation in Materials Science and Engineering. 2018. link Times cited: 10 Abstract: Local stress relaxation mechanisms of crystals are a long-st… read moreAbstract: Local stress relaxation mechanisms of crystals are a long-standing interest in the field of materials physics. Constantly encountered inelastic deformation mechanisms in metals under dynamic loadings, such as dislocation, deformation twinning and phase transition, have been extensively discussed separately or as some of their combinations. Recently, virtual melting is found to be a dominant local stress relaxation mechanism under extreme strain rates. However, these deformation mechanisms have never been investigated in the same metal at an atomic level due to the lack of high pressure interatomic potentials. In this work, an embedded-atom model potential of Pb is developed and tested for high pressure applications. The developed potential of Pb could not only reproduce many energetic, elastic and defective properties at ambient conditions well, but also correctly describe face-centered cubic (fcc)-hexagonal close packed (hcp) and hcp-body-centered cubic phase transition of Pb under high pressures. Shock Hugoniot, as well as equation of states for fcc and hcp phase, also agrees well with the literature ones up to more than 100 GPa. With the developed potential, non-equilibrium molecular dynamic simulations are conducted to investigate dynamic behaviors of Pb single crystal under ramp-shock compressions. Depending on applied strain rates, dislocation-mediated plasticity, phase transition and virtual melting, constantly reported by experiments or theoretical investigations, are observed in our results. Additionally, a new phase transition mechanism of Pb subjected to the ramp compressions is uncovered. read less NOT USED (high confidence) J. F. Tang et al., “Shock wave propagation, plasticity, and void collapse in open-cell nanoporous Ta.,” Physical chemistry chemical physics : PCCP. 2018. link Times cited: 16 Abstract: We systematically investigate the wave propagation, plastici… read moreAbstract: We systematically investigate the wave propagation, plasticity and void collapse, as well as the effects of porosity, specific surface area and impact velocity, in a set of open-cell nanoporous Ta, during shock compression, via performing large-scale non-equilibrium molecular dynamics simulations. The shock wave propagation presents an impedance, sensitive to porosity, but not to specific surface area. Such surprising phenomena are due to the similar sensitivities in density and stress variations to porosity or specific surface area. Upon impact, shock front shapes change from ramped to steep ones, with increasing porosity, specific surface area or impact velocity, owing to the transition from the heterogeneous to homogeneous plasticity along transverse directions. This transition of plasticity arises by (i) the strong impedance on large deformation bands as porosity increases; and (ii) the transition from deformation twinning to dislocation slips, and to amorphization, as the specific surface area or impact velocity increases. Shock-induced plasticity, including their nucleation, growth and interactions, also facilitates the collapse of voids. read less NOT USED (high confidence) H. Lim, J. Carroll, C. Battaile, S. Chen, A. P. Moore, and J. M. D. Lane, “Anisotropy and Strain Localization in Dynamic Impact Experiments of Tantalum Single Crystals,” Scientific Reports. 2018. link Times cited: 11 NOT USED (high confidence) P. Wen, B. Demaske, D. Spearot, and S. Phillpot, “Shock compression of CuxZr100−x metallic glasses from molecular dynamics simulations,” Journal of Materials Science. 2018. link Times cited: 21 NOT USED (high confidence) Y. Tang, “Uncovering the inertia of dislocation motion and negative mechanical response in crystals,” Scientific Reports. 2018. link Times cited: 19 NOT USED (high confidence) D. Li, B. Reich, and D. Brenner, “Using spatial cross-correlation image analysis to characterize the influence of strain rate on plastic damage in molecular dynamics simulations,” Modelling and Simulation in Materials Science and Engineering. 2017. link Times cited: 0 Abstract: We demonstrate how spatial cross-correlation image analysis … read moreAbstract: We demonstrate how spatial cross-correlation image analysis can be used to characterize the strain rate dependence of simulated plastic damage for three systems, two copper bi-crystals containing complementary tilt grain boundaries, and a copper crystal without a grain boundary strained along the [011] direction. Distributions of cross-correlation coefficients (CCs) generated within the same system and strain rate are used to characterize the range of different types of damage observed, while CC distributions generated between the same system but at different strain rates indicate the degree of similarity of the damage generated between strain rates. For both bi-crystals, the CC distributions indicate a broader range of damage configurations as strain rate decreased. For a 15° tilt angle CC distributions generated between the damage configurations at the highest and the lowest strain rates indicate a common set of damage configurations, while for the 45° tilt angle the same analysis suggested comparatively fewer similar damage configurations. In contrast, lower strain rates for the system without initial grain boundaries resulted in far fewer distinct damage configurations and a high degree of matching between the similar configurations. In this case the damage is composed of ordered stacking faults along the (111) planes. read less NOT USED (high confidence) G. Agarwal, R. Valisetty, R. Namburu, A. Rajendran, and A. Dongare, “The Quasi-Coarse-Grained Dynamics Method to Unravel the Mesoscale Evolution of Defects/Damage during Shock Loading and Spall Failure of Polycrystalline Al Microstructures,” Scientific Reports. 2017. link Times cited: 24 NOT USED (high confidence) C. Ma, G.-xiang Wang, C. Ye, and Y. Dong, “Shocking of metallic glass to induce microstructure heterogeneity: A molecular dynamics study,” Journal of Applied Physics. 2017. link Times cited: 10 Abstract: Surface severe plastic deformation (SSPD) has been demonstra… read moreAbstract: Surface severe plastic deformation (SSPD) has been demonstrated to improve the ductility of metallic glass. The physical interpretation, however, remains on the phenomenological level. In this study, a molecular dynamics (MD) simulation is carried out to elucidate the molecular mechanisms underlying the improvement in ductility. MD simulation reveals that shock waves resulting from SSPD can induce pre-deformed atoms, which are randomly embedded in the matrix of the metallic glass. The pre-deformed atoms have similar stress distribution and short-order structure as the matrix atoms, but with a larger atomic volume. When subjected to tensile or compressive stress, more shear bands are promoted by the pre-deformed atoms in the shock-treated sample as compared to the untreated one. The randomly distributed shear bands were found to experience more interactions, which delayed the catastrophic fracture, leading to increased ductility.Surface severe plastic deformation (SSPD) has been demonstrated to improve the ductility of metallic glass. The physical interpretation, however, remains on the phenomenological level. In this study, a molecular dynamics (MD) simulation is carried out to elucidate the molecular mechanisms underlying the improvement in ductility. MD simulation reveals that shock waves resulting from SSPD can induce pre-deformed atoms, which are randomly embedded in the matrix of the metallic glass. The pre-deformed atoms have similar stress distribution and short-order structure as the matrix atoms, but with a larger atomic volume. When subjected to tensile or compressive stress, more shear bands are promoted by the pre-deformed atoms in the shock-treated sample as compared to the untreated one. The randomly distributed shear bands were found to experience more interactions, which delayed the catastrophic fracture, leading to increased ductility. read less NOT USED (high confidence) H. Cho, C. Bronkhorst, H. Mourad, J. Mayeur, and D. Luscher, “Anomalous plasticity of body-centered-cubic crystals with non-Schmid effect,” International Journal of Solids and Structures. 2017. link Times cited: 36 NOT USED (high confidence) S. Kumar and S. Das, “A triaxial tensile deformation-induced nanoporous structure of aluminium: estimation of surface area, solid volume, and dimensionless aspect ratio.,” Physical chemistry chemical physics : PCCP. 2017. link Times cited: 4 Abstract: Nanoporous aluminium has great importance for large scale pr… read moreAbstract: Nanoporous aluminium has great importance for large scale production of automobile and aerospace spare parts due to its lightweight and non-corrosive nature. It is also suitable for various packaging applications of edible things, electronic components, and medicines. We have used triaxial tensile deformation methodology to create a nanoporous structure of aluminium using molecular dynamics simulation. The surface area and solid volume have been calculated to characterize the 3-D nanoporous structure of aluminium. We have quantitatively characterized the growth and coalescences of the nanoporous structure via estimation of the number of nanopores, nanopore diameters, and dimensionless aspect-ratios (surface area to volume ratio). A high aspect ratio indicates a large number of tiny nanopores in the 3-D nanoporous structure of aluminium. We have found that crystalline aluminium (under ambient condition) significantly depicts a smaller aspect ratio as compared to amorphous aluminium during triaxial tensile deformation. We believe that the results of this study will provide new understanding to the researchers for the design and characterization of nanoporous metals. read less NOT USED (high confidence) K. Wang, J. Chena, X. Zhang, and W. Zhu, “Interactions between coherent twin boundaries and phase transition of iron under dynamic loading and unloading,” Journal of Applied Physics. 2017. link Times cited: 19 Abstract: Phase transitions and deformation twins are constantly repor… read moreAbstract: Phase transitions and deformation twins are constantly reported in many BCC metals under high pressure, whose interactions are of fundamental importance to understand the strengthening mechanism of these metals under extreme conditions. However, the interactions between twins and phase transition in BCC metals remain largely unexplored. In this work, interactions between coherent twin boundaries and α ↔ e phase transition of iron are investigated using both non-equilibrium molecular dynamics simulations and the nudged elastic band method. Mechanisms of both twin-assisted phase transition and reverse phase transition are studied, and orientation relationships between BCC and HCP phases are found to be 111¯BCC||1¯21¯0HCP and 11¯0BCC||0001HCP for both cases. The twin boundary corresponds to 101¯0HCP after the phase transition. It is amazing that the reverse transition seems to be able to “memorize” and recover the initial BCC twins. The memory would be partly lost when plastic slips take place in the HCP pha... read less NOT USED (high confidence) L. Hale and C. Becker, “Vacancy dissociation in body-centered cubic screw dislocation cores,” Computational Materials Science. 2017. link Times cited: 9 NOT USED (high confidence) G. Agarwal and A. Dongare, “Modeling the thermodynamic behavior and shock response of Ti systems at the atomic scales and the mesoscales,” Journal of Materials Science. 2017. link Times cited: 20 NOT USED (high confidence) M. Tang, L. Wang, and S. Luo, “Loading-path dependent deformation of nanocrystalline Ta under single- and double-shock, and quasi-isentropic compression,” Journal of Applied Physics. 2017. link Times cited: 30 Abstract: We investigate dynamic deformation of nanocrystalline Ta und… read moreAbstract: We investigate dynamic deformation of nanocrystalline Ta under single- and double-shock, and quasi-isentropic compression, with large-scale molecular dynamics simulations. Orientation mapping, selected area electron diffraction, and x-ray diffraction are implemented for microstructure analysis. Different deformation modes are found for different loading paths, and are attributed to the differences in temperature rise induced by dynamic compression. For sufficiently strong shocks, catastrophic activation of slip systems and their growth in single-shock loading with the largest temperature rise lead to amorphization and recrystallization, while stacking faults and dislocation slip dominate deformation in double-shock loading with intermediate temperature rise, and deformation twinning is the principal mode in quasi-isentropic loading with the least temperature rise. read less NOT USED (high confidence) Y. Hu et al., “Superplastic Formation of Metal Nanostructure Arrays with Ultrafine Gaps,” Advanced Materials. 2016. link Times cited: 21 Abstract: Laser shock compression of plasmonic nanoarrays results in u… read moreAbstract: Laser shock compression of plasmonic nanoarrays results in ultrafine tunable line-gaps at sub-10 nm scale by collaborative superplastic flow. From molecular dynamics analysis, the metal nanostructures change from crystalline to liquid-like metals, expanding quickly but never fusing together, even when they are very close. This technique enables good tunability of surface plasmon resonances and significantly enhanced local fields. read less NOT USED (high confidence) K. Wang, W. Zhu, S. Xiao, J. Chen, and W. Hu, “A new embedded-atom method approach based on the pth moment approximation,” Journal of Physics: Condensed Matter. 2016. link Times cited: 5 Abstract: Large scale atomistic simulations with suitable interatomic … read moreAbstract: Large scale atomistic simulations with suitable interatomic potentials are widely employed by scientists or engineers of different areas. The quick generation of high-quality interatomic potentials is urgently needed. This largely relies on the developments of potential construction methods and algorithms in this area. Quantities of interatomic potential models have been proposed and parameterized with various methods, such as the analytic method, the force-matching approach and multi-object optimization method, in order to make the potentials more transferable. Without apparently lowering the precision for describing the target system, potentials of fewer fitting parameters (FPs) are somewhat more physically reasonable. Thus, studying methods to reduce the FP number is helpful in understanding the underlying physics of simulated systems and improving the precision of potential models. In this work, we propose an embedded-atom method (EAM) potential model consisting of a new manybody term based on the pth moment approximation to the tight binding theory and the general transformation invariance of EAM potentials, and an energy modification term represented by pairwise interactions. The pairwise interactions are evaluated by an analytic-numerical scheme without the need to know their functional forms a priori. By constructing three potentials of aluminum and comparing them with a commonly used EAM potential model, several wonderful results are obtained. First, without losing the precision of potentials, our potential of aluminum has fewer potential parameters and a smaller cutoff distance when compared with some constantly-used potentials of aluminum. This is because several physical quantities, usually serving as target quantities to match in other potentials, seem to be uniquely dependent on quantities contained in our basic reference database within the new potential model. Second, a key empirical parameter in the embedding term of the commonly used EAM model is found to be related to the effective order of moments of local density of states. This may provide a way to improve the precision of EAM potentials further through more precise approximations to tight binding theory. In addition, some critical details about construction procedures are discussed. read less NOT USED (high confidence) M. Javanbakht and V. Levitas, “Phase field approach to dislocation evolution at large strains: Computational aspects,” International Journal of Solids and Structures. 2016. link Times cited: 1 NOT USED (high confidence) C. Liu, C. Xu, Y. Cheng, X.-R. Chen, and L. Cai, “Melting curves and structural properties of tantalum from the modified-Z method,” Journal of Applied Physics. 2015. link Times cited: 6 Abstract: The melting curves and structural properties of tantalum (Ta… read moreAbstract: The melting curves and structural properties of tantalum (Ta) are investigated by molecular dynamics simulations combining with potential model developed by Ravelo et al. [Phys. Rev. B 88, 134101 (2013)]. Before calculations, five potentials are systematically compared with their abilities of producing reasonable compressional and equilibrium mechanical properties of Ta. We have improved the modified-Z method introduced by Wang et al. [J. Appl. Phys. 114, 163514 (2013)] by increasing the sizes in Lx and Ly of the rectangular parallelepiped box (Lx = Ly ≪ Lz). The influences of size and aspect ratio of the simulation box to melting curves are also fully tested. The structural differences between solid and liquid are detected by number density and local-order parameters Q6. Moreover, the atoms' diffusion with simulation time, defects, and vacancies formations in the sample are all studied by comparing situations in solid, solid-liquid coexistence, and liquid state. read less NOT USED (high confidence) G. P. P. Pun, K. Darling, L. Kecskes, and Y. Mishin, “Angular-dependent interatomic potential for the Cu–Ta system and its application to structural stability of nano-crystalline alloys,” Acta Materialia. 2015. link Times cited: 92 NOT USED (high confidence) E. Hahn and M. Meyers, “Grain-size dependent mechanical behavior of nanocrystalline metals,” Materials Science and Engineering A-structural Materials Properties Microstructure and Processing. 2015. link Times cited: 162 NOT USED (high confidence) Y. Fu, J. Michopoulos, and J. H. Song, “Dynamics response of polyethylene polymer nanocomposites to shock wave loading,” Journal of Polymer Science Part B. 2015. link Times cited: 24 Abstract: The shock response of polyethylene polymer modified by nanop… read moreAbstract: The shock response of polyethylene polymer modified by nanoparticles (NP) is investigated using a coarse-grained molecular dynamics simulation. The us-up Hugoniot analysis yields a linear relationship under the range of particle velocity investigated, in agreement with previous simulation and experimental results. NP addition improves the mechanical properties of the composites, as reflected by the increased Young's modulus and yield strength especially in the case of shorter chain length of polymer. This is directly related to the increased shock impedance with NP volume fraction, as demonstrated by the enhanced pressure in the shocked state, slightly reduced microscopic deformation, and increased shock velocity. The layered structure with alternate soft and hard regions, with NP addition only in the hard regions, leads to significantly enhanced microscopic deformation in the soft regions. It is also important that the shock impedance difference between the soft and hard region to be large enough to facilitate the energy absorption through plastic deformation in the soft regions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1292–1302 read less NOT USED (high confidence) R. Xia, R. Wu, Y. Liu, and X. Y. Sun, “The Role of Computer Simulation in Nanoporous Metals—A Review,” Materials. 2015. link Times cited: 28 Abstract: Nanoporous metals (NPMs) have proven to be all-round candida… read moreAbstract: Nanoporous metals (NPMs) have proven to be all-round candidates in versatile and diverse applications. In this decade, interest has grown in the fabrication, characterization and applications of these intriguing materials. Most existing reviews focus on the experimental and theoretical works rather than the numerical simulation. Actually, with numerous experiments and theory analysis, studies based on computer simulation, which may model complex microstructure in more realistic ways, play a key role in understanding and predicting the behaviors of NPMs. In this review, we present a comprehensive overview of the computer simulations of NPMs, which are prepared through chemical dealloying. Firstly, we summarize the various simulation approaches to preparation, processing, and the basic physical and chemical properties of NPMs. In this part, the emphasis is attached to works involving dealloying, coarsening and mechanical properties. Then, we conclude with the latest progress as well as the future challenges in simulation studies. We believe that highlighting the importance of simulations will help to better understand the properties of novel materials and help with new scientific research on these materials. read less NOT USED (high confidence) W. Jian, X. Yao, L. Wang, X. C. Tang, and S. Luo, “Short- and medium-range orders in Cu46Zr54 metallic glasses under shock compression,” Journal of Applied Physics. 2015. link Times cited: 26 Abstract: We investigate short- and medium-range orders in Cu46Zr54 me… read moreAbstract: We investigate short- and medium-range orders in Cu46Zr54 metallic glasses, as represented by icosahedra and icosahedron networks, respectively, under shock compression with molecular dynamics simulations. Complementary isothermal compression and isobaric heating simulations reveal that compression below 60 GPa gives rise to increased coordination and thus high-coordination-number Voronoi polyhedra, such as icosahedra; however, pressure-induced collapse or thermal disintegration of icosahedra (and subsequently, icosahedron networks) occurs at pressures above 60 GPa or at melting, accompanied by free volume increase. The evolutions of the short- and medium-range orders upon shock loading are the effects of compression combined with shock-induced melting. The structural changes are partially reversible for weak shocks without melting (below 60 GPa) and irreversible for strong shocks. Crystallization does not occur under isothermal or shock compression at molecular dynamics scales. read less NOT USED (high confidence) P. Pokatashkin, A. Kuksin, and A. Yanilkin, “Angular dependent potential for α-boron and large-scale molecular dynamics simulations,” Modelling and Simulation in Materials Science and Engineering. 2015. link Times cited: 9 Abstract: Both quantum mechanical and molecular-dynamics (MD) simulati… read moreAbstract: Both quantum mechanical and molecular-dynamics (MD) simulations of α-boron are done at this work. Angular dependent interatomic potential (ADP) for boron is obtained using force-matching technique. Fitting data are based on ab initio results within −20..100 GPa pressure range and temperatures up to 2000 K. Characteristics of α-boron, obtained using ADP potential such as bond lengths at equilibrium condition, bulk modulus, pressure-volume relations, Gruneisen coefficient, thermal expansion coefficient are in good agreement with both ab initio data, obtained in this work and known experimental data. As an example of application, the propagation of shock waves through a single crystal of α-boron is also explored by large-scale MD simulations. read less NOT USED (high confidence) S. Goel, B. Beake, C. Chan, N. Faisal, and N. Dunne, “Twinning anisotropy of tantalum during nanoindentation,” Materials Science and Engineering A-structural Materials Properties Microstructure and Processing. 2015. link Times cited: 62 NOT USED (high confidence) L. Wang, Y. Cai, F. Zhao, D. Fan, and S. Luo, “Shock-induced deformation of nanocrystalline Al: Characterization with orientation mapping and selected area electron diffraction,” Journal of Applied Physics. 2015. link Times cited: 33 Abstract: We investigate shock-induced deformation of columnar nanocry… read moreAbstract: We investigate shock-induced deformation of columnar nanocrystalline Al with large-scale molecular dynamics simulations and implement orientation mapping (OM) and selected area electron diffraction (SAED) for microstructural analysis. Deformation mechanisms include stacking fault formation, pronounced twinning, dislocation slip, grain boundary (GB) sliding and migration, and lattice or partial grain rotation. GBs and GB triple junctions serve as the nucleation sites for crystal plasticity including twinning and dislocations, due to GB weakening, and stress concentrations. Grains with different orientations exhibit different densities of twins or stacking faults nucleated from GBs. GB migration occurs as a result of differential deformation between two grains across the GB. High strain rates, appropriate grain orientation and GBs contribute to deformation twinning. Upon shock compression, intra-grain dislocation and twinning nucleated from GBs lead to partial grain rotation and the formation of subgrains, ... read less NOT USED (high confidence) R. Zhang, T. Germann, X.-Y. Liu, J. Wang, and I. Beyerlein, “Layer size effect on the shock compression behavior of fcc–bcc nanolaminates,” Acta Materialia. 2014. link Times cited: 50 NOT USED (high confidence) J. Zhang, P. S. Branicio, and D. Srolovitz, “Planar fault energies of copper at large strain: A density functional theory study,” Journal of Applied Physics. 2014. link Times cited: 3 Abstract: We present density functional theory calculations of the ext… read moreAbstract: We present density functional theory calculations of the extrinsic stacking fault energy γesf, twin fault energy γtf, and unstable stacking fault energy γusf of copper under large strains, up to ± 10%. The calculated values of γesf, γtf, and γusf for unstrained Cu are 41.8 mJ/m2, 20.2 mJ/m2, and 163.4 mJ/m2, respectively, in good agreement with experimental data and theoretical results. Four different types of strains are applied: (i) volumetric strain; (ii) uniaxial strain perpendicular to the fault plane; (iii) uniaxial strains parallel to the fault plane; and (iv) shear strains across the fault planes. We find that γesf, γtf, and γusf are strongly dependent on the magnitude and type of strain, challenging the common conception that they are constant material properties. The predicted strong strain dependencies provide useful insight into the deformation mechanisms of copper under high pressure and shock conditions and provide essential data to improve current Cu empirical potentials. read less NOT USED (high confidence) C. Ruestes et al., “Atomistic simulation of tantalum nanoindentation: Effects of indenter diameter, penetration velocity, and interatomic potentials on defect mechanisms and evolution,” Materials Science and Engineering A-structural Materials Properties Microstructure and Processing. 2014. link Times cited: 95 NOT USED (high confidence) D. Sun, “Proliferation of Twinning in Metals: Application to Magnesium Alloys.” 2018. link Times cited: 2 Abstract: In the search for new alloys with a great strength-to-weight… read moreAbstract: In the search for new alloys with a great strength-to-weight ratio, magnesium has emerged at the forefront. With a strength rivaling that of steel and aluminum alloys --- materials which are deployed widely in real world applications today --- but only a fraction of the density, magnesium holds great promise in a variety of next-generation applications. Unfortunately, the widespread adoption of magnesium is hindered by the fact that it fails in a brittle fashion, which is undesirable when it comes to plastic deformation mechanisms. Consequently, one must design magnesium alloys to navigate around this shortcoming and fail in a more ductile fashion. However, such designs are not possible without a thorough understanding of the underlying mechanisms of deformation in magnesium, which is somewhat contested at the moment. In addition to slip, which is one of the dominant mechanisms in metallic alloys, a mechanism known as twinning is also present, especially in hexagonal close-packed (HCP) materials such as magnesium. Twinning involves the reorientation of the material lattice about a planar discontinuity and has been shown as one of the preferred mechanisms by which magnesium accommodates out-of-plane deformation. Unfortunately, twinning is not particularly well-understood in magnesium, and needs to be addressed before progress can be made in materials design. In particular, though two specific modes of twinning have been acknowledged, various works in the literature have identified a host of additional modes, many of which have been cast aside as "anomalous" observations. To this end, we introduce a new framework for predicting the modes by which a material can twin, for any given material. Focusing on magnesium, we begin our investigation by introducing a kinematic framework that predicts novel twin configurations, cataloging these twins modes by their planar normal and twinning shear. We then subject the predicted twin modes to a series of atomistic simulations, primarily in molecular statics but with supplementary calculations using density functional theory, giving us insight on both the energy of the twin interface and barriers to formation. We then perform a stress analysis and identify the twin modes which are most likely to be activated, thus finding the ones most likely to affect the yield surface of magnesium. Over the course of our investigation, we show that many different modes actually participate on the yield surface of magnesium; the two classical modes which are accepted by the community are confirmed, but many additional modes --- some of which are close to modes which have been previously regarded as anomalies --- are also observed. We also perform some extensional work, showing the flexibility of our framework in predicting twins in other materials and in other environments and highlighting the complicated nature of twinning, especially in HCP materials. read less NOT USED (high confidence) C. Liu, C. Xu, Y. Cheng, X.-R. Chen, and L. Cai, “The effect of vacancies on melting properties of tantalum via molecular dynamics simulations,” Applied Physics A. 2015. link Times cited: 9 |
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