LAMMPS ReaxFF potential for B4C developed by An and Goddard (2015) v000

An, Q.; William A. Goddard

doi:10.25950/d253fc36

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Sim_LAMMPS_ReaxFF_AnGoddard_2015_BC__SM_389039364091_000

Interatomic potential for Boron (B), Carbon (C).
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Title A single sentence description.	LAMMPS ReaxFF potential for B4C developed by An and Goddard (2015) v000
Description	ReaxFF potential for shock/non-equilibrium studies of boron carbide
Species The supported atomic species.	B, C
Disclaimer A statement of applicability provided by the contributor, informing users of the intended use of this KIM Item.	None
Content Origin	“Atomistic Origin of Brittle Failure of Boron Carbide from Large-Scale Reactive Dynamics Simulations: Suggestions toward Improved Ductility”  DOI: 10.1103/PhysRevLett.115.105501

Contributor	Kimia Ghaffari
Maintainer	Kimia Ghaffari
Developer	An, Q. William A. Goddard
Published on KIM	2023
How to Cite	This Simulator Model originally published in [1] is archived in OpenKIM [2-4]. [1] An Q, Goddard WA. Atomistic Origin of Brittle Failure of Boron Carbide from Large-Scale Reactive Dynamics Simulations: Suggestions toward Improved Ductility. Phys Rev Lett [Internet]. 2015Aug;115(10):105501. Available from: https://link.aps.org/doi/10.1103/PhysRevLett.115.105501 doi:10.1103/PhysRevLett.115.105501 — (Primary Source) A primary source is a reference directly related to the item documenting its development, as opposed to other sources that are provided as background information. [2] An Q, Goddard WA. LAMMPS ReaxFF potential for B4C developed by An and Goddard (2015) v000. OpenKIM; 2023. doi:10.25950/d253fc36 [3] Tadmor EB, Elliott RS, Sethna JP, Miller RE, Becker CA. The potential of atomistic simulations and the Knowledgebase of Interatomic Models. JOM. 2011;63(7):17. doi:10.1007/s11837-011-0102-6 [4] Elliott RS, Tadmor EB. Knowledgebase of Interatomic Models (KIM) Application Programming Interface (API). OpenKIM; 2011. doi:10.25950/ff8f563a Click here to download the above citation in BibTeX format.
Citations This panel presents information regarding the papers that have cited the interatomic potential (IP) whose page you are on. The OpenKIM machine learning based Deep Citation framework is used to determine whether the citing article actually used the IP in computations (denoted by "USED") or only provides it as a background citation (denoted by "NOT USED"). For more details on Deep Citation and how to work with this panel, click the documentation link at the top of the panel. The word cloud to the right is generated from the abstracts of IP principle source(s) (given below in "How to Cite") and the citing articles that were determined to have used the IP in order to provide users with a quick sense of the types of physical phenomena to which this IP is applied. The bar chart shows the number of articles that cited the IP per year. Each bar is divided into green (articles that USED the IP) and blue (articles that did NOT USE the IP). 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See the Deep Citation documentation for more information. 103 Citations (91 used) Show Model Used Show All Help us to determine which of the papers that cite this potential actually used it to perform calculations. If you know, click the . K. Ramesh et al., “Models for the behavior of boron carbide in extreme dynamic environments,” Journal of the American Ceramic Society. 2021. link Times cited: 9 Y. Shen, M. Yang, W. Goddard, and Q. An, “Strengthening boron carbide by doping Si into grain boundaries,” Journal of the American Ceramic Society. 2021. link Times cited: 1 J. Clayton, M. Guziewski, J. Ligda, R. B. Leavy, and J. Knap, “A Multi-Scale Approach for Phase Field Modeling of Ultra-Hard Ceramic Composites,” Materials. 2021. link Times cited: 7 Abstract: Diamond-silicon carbide (SiC) polycrystalline composite blen… read more Abstract: Diamond-silicon carbide (SiC) polycrystalline composite blends are studied using a computational approach combining molecular dynamics (MD) simulations for obtaining grain boundary (GB) fracture properties and phase field mechanics for capturing polycrystalline deformation and failure. An authentic microstructure, reconstructed from experimental lattice diffraction data with locally refined discretization in GB regions, is used to probe effects of local heterogeneities on material response in phase field simulations. The nominal microstructure consists of larger diamond and SiC (cubic polytype) grains, a matrix of smaller diamond grains and nanocrystalline SiC, and GB layers encasing the larger grains. These layers may consist of nanocrystalline SiC, diamond, or graphite, where volume fractions of each phase are varied within physically reasonable limits in parametric studies. Distributions of fracture energies from MD tension simulations are used in the phase field energy functional for SiC-SiC and SiC-diamond interfaces, where grain boundary geometries are obtained from statistical analysis of lattice orientation data on the real microstructure. An elastic homogenization method is used to account for distributions of second-phase graphitic inclusions as well as initial voids too small to be resolved individually in the continuum field discretization. In phase field simulations, SiC single crystals may twin, and all phases may fracture. The results of MD calculations show mean strengths of diamond-SiC interfaces are much lower than those of SiC-SiC GBs. In phase field simulations, effects on peak aggregate stress and ductility from different GB fracture energy realizations with the same mean fracture energy and from different random microstructure orientations are modest. Results of phase field simulations show unconfined compressive strength is compromised by diamond-SiC GBs, graphitic layers, graphitic inclusions, and initial porosity. Explored ranges of porosity and graphite fraction are informed by physical observations and constrained by accuracy limits of elastic homogenization. Modest reductions in strength and energy absorption are witnessed for microstructures with 4% porosity or 4% graphite distributed uniformly among intergranular matrix regions. Further reductions are much more severe when porosity is increased to 8% relative to when graphite is increased to 8%. read less N. Song, Z. Gao, and X. Li, “Tailoring nanocomposite interfaces with graphene to achieve high strength and toughness,” Science Advances. 2020. link Times cited: 33 Abstract: Tailoring the composite interfaces with graphene enabled eff… read more Abstract: Tailoring the composite interfaces with graphene enabled effective utilization of the nanofillers. The nanofiller reinforcing effect in nanocomposites is often far below the theoretically predicted values, largely because of the poor interfacial interaction between the nanofillers and matrix. Here, we report that graphene-wrapped B4C nanowires (B4C-NWs@graphene) empowered exceptional dispersion of nanowires in matrix and superlative nanowire-matrix bonding. The 0.2 volume % B4C-NWs@graphene reinforced epoxy composite exhibited simultaneous enhancements in strength (144.2 MPa), elastic modulus (3.5 GPa), and ductility (15%). Tailoring the composite interfaces with graphene enabled effective utilization of the nanofillers, resulting in two times increase in load transfer efficiency. Molecular dynamics simulations unlocked the shear mixing graphene/nanowire self-assembly mechanism. This low-cost yet effective technique presents unprecedented opportunities for improving nanocomposite interfaces, enabling high load transfer efficiency, and opens up a new path for developing strong and tough nanocomposites. read less T. Cheng, A. Jaramillo-Botero, Q. An, D. Ilyin, S. Naserifar, and W. Goddard, “First principles-based multiscale atomistic methods for input into first principles nonequilibrium transport across interfaces,” Proceedings of the National Academy of Sciences. 2018. link Times cited: 7 Abstract: This issue of PNAS features “nonequilibrium transport and mi… read more Abstract: This issue of PNAS features “nonequilibrium transport and mixing across interfaces,” with several papers describing the nonequilibrium coupling of transport at interfaces, including mesoscopic and macroscopic dynamics in fluids, plasma, and other materials over scales from microscale to celestial. Most such descriptions describe the materials in terms of the density and equations of state rather than specific atomic structures and chemical processes. It is at interfacial boundaries where such atomistic information is most relevant. However, there is not yet a practical way to couple these phenomena with the atomistic description of chemistry. The starting point for including such information is the quantum mechanics (QM). However, practical QM calculations are limited to a hundred atoms for dozens of picoseconds, far from the scales required to inform the continuum level with the proper atomistic description. To bridge this enormous gap, we need to develop practical methods to extend the scale of the atomistic simulation by several orders of magnitude while retaining the level of QM accuracy in describing the chemical process. These developments would enable continuum modeling of turbulent transport at interfaces to incorporate the relevant chemistry. In this perspective, we will focus on recent progress in accomplishing these extensions in first principles-based atomistic simulations and the strategies being pursued to increase the accuracy of very large scales while dramatically decreasing the computational effort. read less X. Song, C. Liu, Q. Li, Y. Ma, and C. Chen, “Intrinsic dense twinning via release of native strain,” Acta Materialia. 2023. link Times cited: 2 J. Y. Li, K. Luo, and Q. An, “Mobile dislocation mediated Hall-Petch and inverse Hall-Petch behaviors in nanocrystalline Al-doped boron carbide,” Journal of the European Ceramic Society. 2023. link Times cited: 0 X. Hu et al., “Amorphous shear bands in crystalline materials as drivers of plasticity,” Nature Materials. 2023. link Times cited: 5 Y. Chen et al., “Cross-interface growth mechanism of nanotwins in extremely high stacking-fault energy ceramic layer,” Acta Materialia. 2023. link Times cited: 0 N. Wang et al., “An Atomistic Study of Plastic Deformation of Smco5 by Amorphous Shear Bands,” SSRN Electronic Journal. 2023. link Times cited: 0 J. Y. Li and Q. An, “Nanotwinning-induced pseudoplastic deformation in boron carbide under low temperature,” International Journal of Mechanical Sciences. 2023. link Times cited: 3 B. Amirian, B. Abali, and J. Hogan, “The study of diffuse interface propagation of dynamic failure in advanced ceramics using the phase-field approach,” Computer Methods in Applied Mechanics and Engineering. 2023. link Times cited: 1 J. Clayton, J. Knap, and R. B. Leavy, “On rate dependence and anisotropy in phase field modeling of polycrystalline fracture,” Mechanics of Materials. 2023. link Times cited: 2 J. Clayton, “Modeling Deformation and Fracture of Boron-Based Ceramics with Nonuniform Grain and Phase Boundaries and Thermal-Residual Stress,” Solids. 2022. link Times cited: 2 Abstract: A phase field framework of elasticity, inelasticity, and fra… read more Abstract: A phase field framework of elasticity, inelasticity, and fracture mechanics is invoked to study the behavior of ceramic materials. Mechanisms addressed by phase field theory include deformation twinning, dislocation slip, amorphization, and anisotropic cleavage fracture. Failure along grain and phase boundaries is resolved explicitly, whereWeibull statistics are used to characterize the surface energies of such boundaries. Residual stress incurred by mismatching coefficients of thermal expansion among phases is included. Polycrystalline materials of interest are the ultra-hard ceramics boron carbide (B4C) and boron carbide-titanium diboride (B4C-TiB2), the latter a dual-phase composite. Recent advancements in processing technology enable the production of these materials via spark-plasma sintering (SPS) at nearly full theoretical density. Numerical simulations invoking biaxial loading (e.g., pure shear) demonstrate how properties and mechanisms at the scale of the microstructure influence overall strength and ductility. In agreement with experimental inferences, simulations show that plasticity is more prevalent in the TiB2 phase of the composite and reduces the tendency for transgranular fracture. The composite demonstrates greater overall strength and ductility than monolithic B4C in both simulations and experiments. Toughening of the more brittle B4C phase from residual stress, in addition to crack mitigation from the stronger and more ductile TiB2 phase are deemed advantageous attributes of the composite. read less X. Li, X. Yang, H. Mei, L. Liu, S. Xu, and J. Zhang, “Boron carbide nanopillars under impact loading: Mechanical response and amorphous bands formation mechanism,” Computational Materials Science. 2022. link Times cited: 0 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 J. Clayton, R. B. Leavy, and J. Knap, “Phase field mechanics of residually stressed ceramic composites,” Philosophical Magazine. 2022. link Times cited: 3 Abstract: ABSTRACT A phase field theory for crystalline solids account… read more Abstract: ABSTRACT A phase field theory for crystalline solids accounting for thermoelasticity, fracture, twinning, and limited slip is presented. Residual stresses are incorporated via referencing thermoelastic strain to a reference state that is not always stress-free. Rate dependence, dissipated energy, and residual strain energy (possibly degraded by local fracture) are included in the theory, with physically valid predictions first verified for homogeneous stress states. A variational form of the model is implemented in finite element (FE) calculations of three-dimensional (3-D) polycrystalline aggregates consisting of up to two different crystal constituents and a binding matrix along grain and phase boundaries. Model specifics correspond to constituents of boron carbide-titanium diboride (B C-TiB ) ceramic composites. Effects of thermal-residual stresses incurred during processing, as well as other local microstructure properties and physical features, on deformation and failure mechanisms are revealed. Peak aggregate strengths observed for different boundary conditions demonstrate a pressure-dependent failure surface. read less K. Tan et al., “Impacts of defect distribution on the ignition of crystalline explosives: An insight from the overlapping effect,” Energetic Materials Frontiers. 2022. link Times cited: 2 B. Amirian, H. Jafarzadeh, B. Abali, A. Reali, and J. Hogan, “Thermodynamically-consistent derivation and computation of twinning and fracture in brittle materials by means of phase-field approaches in the finite element method,” International Journal of Solids and Structures. 2022. link Times cited: 7 H. C. Cekil and M. Özdemir, “The behaviour of Boron Carbide under shock compression conditions: MD simulation results,” Computational Materials Science. 2022. link Times cited: 3 J. Clayton, “Nonlinear thermodynamic phase field theory with application to fracture and dynamic inelastic phenomena in ceramic polycrystals,” Journal of the Mechanics and Physics of Solids. 2021. link Times cited: 13 C.-J. Wang, K. Luo, J. Wang, and J. Lu, “Carbide-facilitated nanocrystallization of martensitic laths and carbide deformation in AISI 420 stainless steel during laser shock peening,” International Journal of Plasticity. 2021. link Times cited: 59 X. Li, L. Liu, H. Mei, S. Xu, J. Li, and J. Zhang, “The formation mechanisms of amorphous bands of boron carbide nanopillars under uniaxial compressions and their effects on mechanical properties from molecular dynamics simulation,” Computational Materials Science. 2021. link Times cited: 1 J. Li, Q. An, and L. Liu, “Local amorphization in boron carbide at finite temperature: Strategies toward improved ductility,” Physical Review B. 2021. link Times cited: 6 Abstract: Boron carbide (${\mathrm{B}}_{4}\mathrm{C}$) is superhard, b… read more Abstract: Boron carbide (${\mathrm{B}}_{4}\mathrm{C}$) is superhard, but its engineering applications are limited by the abnormal brittle failure arising from amorphous shear band formation. Mitigating the local amorphization is essential to improve the ductility of ${\mathrm{B}}_{4}\mathrm{C}$. Here, we carried out ab initio molecular dynamics (AIMD) simulations to examine the response of ${\mathrm{B}}_{4}\mathrm{C}$ to shear along two plausible slip systems $(001)/[100]$ and $(111)/[11\overline{2}]$ at finite temperature. We found that the icosahedra of ${\mathrm{B}}_{4}\mathrm{C}$ gradually deconstruct at finite temperature, resulting in local amorphization, thereby giving rise to a lower stress barrier than that of density functional theory simulations at zero temperature. The deconstruction of the icosahedral clusters arises from the interaction with the neighboring chains. The failure mechanism at the finite temperature suggested that the local amorphization can be suppressed by altering the structure of the 12-atom icosahedron and the 3-atom chain of ${\mathrm{B}}_{4}\mathrm{C}$. To demonstrate this, we replaced the ${\mathrm{B}}_{11}{\mathrm{C}}^{\mathrm{P}}$ icosahedron in ${\mathrm{B}}_{4}\mathrm{C}$ with ${\mathrm{B}}_{12}$ icosahedron to form boron-rich boron carbide (${\mathrm{B}}_{13}{\mathrm{C}}_{2}$) and then performed the same shear deformations. We found that local amorphization significantly decreases, which results from the modified icosahedral interaction. We also altered the 3-atom C-B-C chain to the 2-atom P-P chain and found that the accumulated shear stress can be released through icosahedral slipping, which is achieved by breaking the chains. The icosahedral slipping then prevents the destruction of icosahedra under shear deformations, expected to improve the ductility. Our results demonstrate two design strategies toward improved ductility of ${\mathrm{B}}_{4}\mathrm{C}$: (1) boron enrichment can alleviate amorphous shear band formation in boron carbide, and (2) altering the 3-atom chain to a 2-atom chain and meanwhile decreasing the strength of the chain to make it less stable than the icosahedron cage may lead to an icosahedral-slipping-dominated mechanism, thereby avoiding icosahedral fracture. read less X. Ren, X. Yan, L. Wang, Y. Zhao, and S. Wang, “Strengthening Superhard Materials by Nanostructure Engineering,” Journal of Superhard Materials. 2021. link Times cited: 0 A. Zare et al., “Mechanical characterization of boron carbide single crystals,” Journal of the American Ceramic Society. 2021. link Times cited: 5 K. Xie et al., “Experimental observations of amorphization in multiple generations of boron carbide,” Journal of the American Ceramic Society. 2021. link Times cited: 5 S. Z. Chavoshi, P. S. Branicio, and Q. An, “Transition between Hall-Petch and inverse Hall-Petch behavior in nanocrystalline silicon carbide,” Physical Review Materials. 2021. link Times cited: 9 Abstract: Despite much experimental and simulation effort, the existen… read more Abstract: Despite much experimental and simulation effort, the existence of a Hall-Petch to inverse Hall-Petch transition in nanocrystalline ceramics remains elusive. By employing molecular dynamics simulations, we unambiguously reveal a transition from strengthening to softening in the shear deformation of nanocrystalline silicon carbide ceramics as a function of grain size. Results show a well-defined maximum in the shear strength for grain sizes in the range 6.2 to 7.7 nm. Further decrease in grain size leads to diminishing strength, consistent with an inverse Hall-Petch behavior. As grain size is reduced the increasing grain boundary (GB) regions lead to homogenization of shear stresses across the microstructure, allowing for lower local shear stress levels at higher macroscopically applied stresses. This delays shear localization within GB regions, preventing cavitation, nanocracking, and premature failure, and is responsible for the observed Hall-Petch behavior. In contrast, at grain sizes 6.2 nm, the rather compliant nature of the structurally disordered GB regions dominates the mechanical response, reducing the shear strength and triggering a transition into the inverse Hall-Petch behavior. A composite model delineating the transition between Hall-Petch and inverse Hall-Petch behavior is successful at describing the mechanical behavior of nanocrystalline silicon carbide as a function of grain size. read less J. Li, S. Xu, J. Zhang, and L. Liu, “First-Principles Predicting Improved Ductility of Boron Carbide through Element Doping,” Journal of Physical Chemistry C. 2021. link Times cited: 12 Y. Shen, J. Fuller, and Q. An, “Mitigating the formation of amorphous shear band in boron carbide,” Journal of Applied Physics. 2021. link Times cited: 5 Abstract: Boron carbide is super-strong and has many important enginee… read more Abstract: Boron carbide is super-strong and has many important engineering applications such as body armor and cutting tools. However, the extended applications of boron carbide have been limited by its low fracture toughness arising from anomalous brittle failure when subjected to hypervelocity impact or under high pressure. This abnormal brittle failure is directly related to the formation of a tiny amorphous shear band of 2–3 nm in width and several hundred nm in length. In this Perspective, we discuss mitigating the amorphous shear bands in boron carbide from various strategies including microalloying, grain boundary engineering, stoichiometry control, and the addition of a second phase. Combined with recent theoretical and experimental studies, we discuss strategies that can be applied in synthesizing and producing boron carbide-based materials with improved ductility by suppressing the formation of the amorphous shear band. read less K. Reddy et al., “Dislocation-mediated shear amorphization in boron carbide,” Science Advances. 2021. link Times cited: 33 Abstract: A previously unidentified amorphization mechanism of boron c… read more Abstract: A previously unidentified amorphization mechanism of boron carbide yields insights into the failure of superhard materials. The failure of superhard materials is often associated with stress-induced amorphization. However, the underlying mechanisms of the structural evolution remain largely unknown. Here, we report the experimental measurements of the onset of shear amorphization in single-crystal boron carbide by nanoindentation and transmission electron microscopy. We verified that rate-dependent loading discontinuity, i.e., pop-in, in nanoindentation load-displacement curves results from the formation of nanosized amorphous bands via shear amorphization. Stochastic analysis of the pop-in events reveals an exceptionally small activation volume, slow nucleation rate, and lower activation energy of the shear amorphization, suggesting that the high-pressure structural transition is activated and initiated by dislocation nucleation. This dislocation-mediated amorphization has important implications in understanding the failure mechanisms of superhard materials at stresses far below their theoretical strengths. read less M. Chen, Z. Liang, M. Liu, U. P. Kumar, C. Liu, and T. Liang, “First principles study of post-boron carbide phases with icosahedra broken,” Chinese Physics B. 2020. link Times cited: 2 L.-yuan Wang et al., “Novel superhard boron-rich nitrides under pressure,” Science China Materials. 2020. link Times cited: 14 A. Awasthi and G. Subhash, “Deformation behavior and amorphization in icosahedral boron-rich ceramics,” Progress in Materials Science. 2020. link Times cited: 30 O. Bystrenko et al., “Kinetics of bonds at structural breakdown in boron carbide under intensive loads: A molecular dynamics study,” Computational Materials Science. 2020. link Times cited: 2 J. Dai, J. Singh, and N. Yamamoto, “Fabrication and characterization of FAST sintered micro/nano boron carbide composites with enhanced fracture toughness,” Journal of the European Ceramic Society. 2020. link Times cited: 13 H. Luo, H. Zhang, H. Sheng, J. Liu, and I. Szlufarska, “Amorphous shear bands in SmCo5,” Materials Science and Engineering A-structural Materials Properties Microstructure and Processing. 2020. link Times cited: 12 J. Fuller and Q. An, “Room-Temperature Plastic Deformation in Diamond Nanopillars.” 2020. link Times cited: 3 Q. Yang, A. M. Celik, J. Du, J. LaSalvia, C. Hwang, and R. Haber, “Advancing the mechanical properties of Si/B co-doped boron carbide through TiB2 reinforcement,” Materials Letters. 2020. link Times cited: 11 M. Devries, G. Subhash, and A. Awasthi, “Shocked ceramics melt: An atomistic analysis of thermodynamic behavior of boron carbide,” Physical Review B. 2020. link Times cited: 17 Abstract: Macroscale experiments for structural response of materials … read more Abstract: Macroscale experiments for structural response of materials often do not capture deformation features at the atomistic scale. This limitation becomes more pronounced in materials subjected to shock loading, especially in covalently bonded ceramics such as boron carbide, which exhibit a deleterious mechanism called pressure-induced amorphization. Perhaps because ceramics have high thermal resistance, temperature was never considered a prime factor influencing deformation mechanisms, leaving such phenomena unexplained for more than two decades. In this article, we probe fundamental material behavior using molecular dynamics (MD) to link nanoscale thermodynamics to amorphization during shock loading. We have generated Rayleigh lines via MD shock simulations, subsequently constructing the shock Hugoniot, which aligns well with experimental data. We estimate shock-induced temperature in ceramics to be well above their melting point, resolving a plethora of interconnected scientific issues pertaining to anomalous behavior of boron carbide. read less S. Xiang et al., “The effect of boron and aluminum additions on the microstructure of arc‐melted boron carbide,” Journal of the American Ceramic Society. 2020. link Times cited: 3 Abstract: In this work, B 4 C, B 4 C + 5 at.% Al, B 4 C + B, and B 4 C… read more Abstract: In this work, B 4 C, B 4 C + 5 at.% Al, B 4 C + B, and B 4 C + B + 5 at.% Al were arc melted, and the resultant solid products were characterized. Results from x-ray diffraction and scanning electron microscopy showed that adding Al alone in B 4 C did not result in Al-doping; adding Al and B in B 4 C led to Al-doping. Al-doping also changed the wettability, thus the surface energy of boron carbide in the liquid state. Transmission electron microscopy revealed stacking faults are more likely to form in the Al-doped sample, especially in the regions where the Al concentration is high. read less N. Baishnab et al., “Role of generated free radicals in synthesis of amorphous hydrogenated boron carbide from orthocarborane using argon bombardment: a ReaxFF molecular dynamics study,” Materials Research Express. 2020. link Times cited: 0 Abstract: In this study, we modeled and analyzed a critical aspect of … read more Abstract: In this study, we modeled and analyzed a critical aspect of the synthesis process for a-BxC:Hy i.e. the argon bombardment from the ortho-carborane precursor. Utilizing the reactive molecular dynamics simulations, we identified and evaluated the formation of free radicals as a result of ion bombardment. We found that increasing kinetic energy of ions releases an increasing amount of hydrogen. Thus, hydrogen content in the product can be tuned by varying the ion energy. Overall, our approach allows for a better understanding of the mechanism of Ar bombardment and the role of radical species toward the formation of ortho-carborane network. read less R. Khadka, N. Baishnab, G. Opletal, and R. Sakidja, “Study of amorphous boron carbide (a-BxC) materials using Molecular Dynamics (MD) and Hybrid Reverse Monte Carlo (HRMC),” Journal of Non-crystalline Solids. 2020. link Times cited: 5 T. A. Yıldız and M. Durandurdu, “Amorphous boron carbide from ab initio simulations,” Computational Materials Science. 2020. link Times cited: 4 J. Gu et al., “Reactive sintering of B4C-TaB2 ceramics via carbide boronizing: Reaction process, microstructure and mechanical properties,” Journal of Materials Science & Technology. 2019. link Times cited: 19 Q. Yang et al., “Fabrication and characterization of arc melted Si/B co-doped boron carbide,” Journal of The European Ceramic Society. 2019. link Times cited: 13 A. Chauhan, X. Sun, K. Ramesh, and K. Hemker, “Dynamic failure mechanisms of granular boron carbide under multi-axial high-strain-rate loading,” Scripta Materialia. 2019. link Times cited: 9 A. Chauhan, M. Schaefer, R. Haber, and K. Hemker, “Experimental observations of amorphization in stoichiometric and boron-rich boron carbide,” Acta Materialia. 2019. link Times cited: 35 Z. Chao, T. T. Sun, L. Jiang, Z. Zhou, C. Guoqin, and G. Wu, “Ballistic behavior and microstructure evolution of B4C/AA2024 composites,” Ceramics International. 2019. link Times cited: 18 S. Xiang et al., “Tuning the deformation mechanisms of boron carbide via silicon doping,” Science Advances. 2019. link Times cited: 20 Abstract: Si-doped boron carbide could be a promising material for the… read more Abstract: Si-doped boron carbide could be a promising material for the next-generation body armor. Boron carbide suffers from a loss of strength and toughness when subjected to high shear stresses due to amorphization. Here, we report that a small amount of Si doping (~1 atomic %) leads to a substantial decrease in stress-induced amorphization due to a noticeable change of the deformation mechanisms in boron carbide. In the undoped boron carbide, the Berkovich indentation–induced quasi-plasticity is dominated by amorphization and microcracking along the amorphous shear bands. This mechanism resulted in long, distinct, and single-variant shear faults. In contrast, substantial fragmentation with limited amorphization was activated in the Si-doped boron carbide, manifested by the short, diffuse, and multivariant shear faults. Microcracking via fragmentation competed with and subsequently mitigated amorphization. This work highlights the important roles that solute atoms play on the structural stability of boron carbide and opens up new avenues to tune deformation mechanisms of ceramics via doping. read less R. Zhang et al., “First-principles design of strong solids: Approaches and applications,” Physics Reports. 2019. link Times cited: 24 B. Yang et al., “Detwinning Mechanism for Nanotwinned Cubic Boron Nitride with Unprecedented Strength: A First-Principles Study,” Nanomaterials. 2019. link Times cited: 5 Abstract: Synthesized nanotwinned cubic boron nitride (nt-cBN) and nan… read more Abstract: Synthesized nanotwinned cubic boron nitride (nt-cBN) and nanotwinned diamond (nt-diamond) exhibit extremely high hardness and excellent stability, in which nanotwinned structure plays a crucial role. Here we reveal by first-principles calculations a strengthening mechanism of detwinning, which is induced by partial slip on a glide-set plane. We found that continuous partial slip in the nanotwinned structure under large shear strain can effectively delay the structural graphitization and promote the phase transition from twin structure to cubic structure, which helps to increase the maximum strain range and peak stress. Moreover, ab initio molecular dynamics simulation reveals a stabilization mechanism for nanotwin. These results can help us to understand the unprecedented strength and stability arising from the twin boundaries. read less A. Chauhan, M. Schaefer, R. Haber, and K. Hemker, “Observed Mitigation of Local Amorphization in Boron-Rich Boron Carbide,” Materials Engineering eJournal. 2019. link Times cited: 3 Abstract: Boron carbide is extremely hard but has been shown to underg… read more Abstract: Boron carbide is extremely hard but has been shown to undergo stress-induced amorphization when subjected to large nonhydrostatic stresses. This localized amorphization has been associated with the sudden loss of shear strength and poor ballistic performance. Recent quantum mechanics predictions suggest that boron-enrichment may be used to mitigate amorphization in boron carbide. As a means to test this hypothesis, stoichiometric boron carbide (nominally B₄C) and a novel composition of B-rich boron carbide (nominally B_6.3C) were investigated. Nanoindentation followed by Raman spectroscopy revealed an obvious reduction in the Raman peaks associated with amorphization in the B-rich material. Transmission electron microscopy observations of the region below the nanoindents facilitated direct observation of amorphization, confirmed the Raman result that amorphization is reduced in the B-rich specimens, and provided additional insight into deformation mechanisms. It is concluded that boron-rich alloys offer one path to mitigating local amorphization in boron carbide. read less J. D. Clayton, R. B. Leavy, and J. Knap, “Phase field modeling of heterogeneous microcrystalline ceramics,” International Journal of Solids and Structures. 2019. link Times cited: 14 D. Guo and Q. An, “Transgranular amorphous shear band formation in polycrystalline boron carbide,” International Journal of Plasticity. 2019. link Times cited: 12 A. Awasthi and G. Subhash, “High-pressure deformation and amorphization in boron carbide,” Journal of Applied Physics. 2019. link Times cited: 33 Abstract: Icosahedral boron-rich solids fall second in hardness to dia… read more Abstract: Icosahedral boron-rich solids fall second in hardness to diamondlike structures and have been the subject of intense investigations over the past two decades, as they possess low density, high thermal, and mechanical stability at high temperatures, and superior industrial manufacturability. A common deleterious feature called “presssure-induced amorphization,” limits their performance in high-velocity projectile applications. This article discusses spectral characteristics of amorphized states of boron carbide, a common icosahedral boron-rich ceramic, with the goal of understanding the mechanistic layout of pressure-induced amorphization. Mystery has surrounded the appearance of new peaks in Raman spectrum of pressure-induced amorphized boron carbide, but to date, no convincing explanation exists on their origin. Shock studies of boron carbide have proposed phase transformation at high pressures, but to date, no conclusive evidence has been corroborative to prove the existence of new high-pressure phases. We propose a new rationale toward deciphering the amorphization phenomenon in boron carbide centered on a thermodynamic approach to explain atomic interactions in amorphous islands. Quantum mechanical simulations are utilized to understand the impact of stresses on Raman spectra, while results from molecular dynamics (MD) simulations of volumetric compression are used to understand thermodynamic aspects of amorphization. Atomic-level nonbonded interactions from the MD potential are utilized to demonstrate origins of the residual pressure. Combining these efforts, the present study deciphers the connection between deformation behavior of boron carbide at high pressure and its mysterious amorphous Raman spectrum. The approach highlights the importance of meticulously incorporating multiscale modeling considerations in determining accurate material behavior of ultrahard materials. read less M. Devries and G. Subhash, “Influence of carbon nanotubes as secondary phase addition on the mechanical properties and amorphization of boron carbide,” Journal of the European Ceramic Society. 2019. link Times cited: 19 Y. Shen, G. Li, and Q. An, “Enhanced fracture toughness of boron carbide from microalloying and nanotwinning,” Scripta Materialia. 2019. link Times cited: 21 Y. Shen and Q. An, “Brittle failure of orthorhombic borides from first-principles simulations,” Physical Review B. 2018. link Times cited: 1 J. Clayton and J. Knap, “Geometric micromechanical modeling of structure changes, fracture and grain boundary layers in polycrystals,” Journal of Micromechanics and Molecular Physics. 2018. link Times cited: 11 Abstract: A constitutive framework based on concepts from phase field … read more Abstract: A constitutive framework based on concepts from phase field theory and pseudo-Finsler geometry is exercised in numerical simulations of deformation and fracture of ceramic polycrystals. The material system of interest is boron carbide, a hard but brittle ceramic. Some microstructures are enabled with thin layers of a secondary amorphous phase of boron nitride between grains of boron carbide. The constitutive theory accounts for physical mechanisms of twinning, crystal-to-glass phase transformations, cleavage fracture within grains and separation and cavitation at grain boundaries (GBs). According to the generalized Finsler approach, geometric quantities such as the metric tensor and connection coefficients can depend on one or more director vectors, also called internal state vectors, that enter the energy potential in a manner similar to order parameters of phase field models. A partially linearized version of the theory is invoked in finite element simulations of polycrystals, with and without GB layers, subjected to pure shear loading. Effects of grain size and layer properties — thickness, shear modulus and surface energy — are studied parametrically. Results demonstrate that twinning and amorphization occur prominently in nanocrystals but less so in aggregates with larger grains that tend to fail earlier by fracture. Structural changes occur readily in the latter at smaller applied strains only in conjunction with elastic shear softening in localized degraded or damaged regions. Hall–Petch scaling of peak shear strength with grain size is observed. Strength is increased via addition of amorphous layers that shift the failure mode from transgranular to intergranular and further by cavity expansion in layers that induces local elastic compression and suppresses crack extension. Stiff layers provide the largest peak strength enhancement, while elastically compliant layers may improve toughness and strength in the softening regime. read less A. Khan et al., “Locating Si atoms in Si-doped boron carbide: A route to understand amorphization mitigation mechanism,” Acta Materialia. 2018. link Times cited: 34 S. Dyachkov, A. Parshikov, M. S. Egorova, S. Grigoryev, V. Zhakhovsky, and S. Medin, “Explicit failure model for boron carbide ceramics under shock loading,” Journal of Applied Physics. 2018. link Times cited: 11 Abstract: Ceramic materials have a long-term industrial demand due to … read more Abstract: Ceramic materials have a long-term industrial demand due to their high mechanical hardness and chemical and temperature resistance. They are brittle and tend to lose strength under heavy loads which complicates the development of a comprehensive material model for simulation of engineering prototypes containing ceramic parts. We developed an improved failure model of ceramics based on the well-known Johnson–Holmquist approach. This model redefines the damage rate equation using a consistent definition of the total plastic strain in the failed material. It reduces the number of free model parameters and enables the plastic strain to be explicitly accumulated during the failure process. The corresponding non-iterative algorithm utilizing this explicit failure model is developed. It is successfully validated by simulation of the wave profiles obtained in plate-impact experiments with boron carbide using the contact smoothed particle hydrodynamic method.Ceramic materials have a long-term industrial demand due to their high mechanical hardness and chemical and temperature resistance. They are brittle and tend to lose strength under heavy loads which complicates the development of a comprehensive material model for simulation of engineering prototypes containing ceramic parts. We developed an improved failure model of ceramics based on the well-known Johnson–Holmquist approach. This model redefines the damage rate equation using a consistent definition of the total plastic strain in the failed material. It reduces the number of free model parameters and enables the plastic strain to be explicitly accumulated during the failure process. The corresponding non-iterative algorithm utilizing this explicit failure model is developed. It is successfully validated by simulation of the wave profiles obtained in plate-impact experiments with boron carbide using the contact smoothed particle hydrodynamic method. read less J. Clayton, “Generalized pseudo-Finsler geometry applied to the nonlinear mechanics of torsion of crystalline solids,” International Journal of Geometric Methods in Modern Physics. 2018. link Times cited: 8 Abstract: A continuum theory of the mechanical behavior of solid mater… read more Abstract: A continuum theory of the mechanical behavior of solid materials is presented wherein fundamental geometric quantities such as the metric tensor and connection coefficients can depend on one or mor... read less J. Li, S. Xu, L. Liu, Z. Wang, J. Zhang, and Q. Liu, “Mechanism for amorphization of boron carbide under complex stress conditions,” Materials Research Express. 2018. link Times cited: 14 Abstract: As an excellent material, the application of boron carbide (… read more Abstract: As an excellent material, the application of boron carbide (B4C) is limited by pressure-induced amorphization. To understand the mechanism for amorphization in B4C, first-principles methods based on density functional theory were employed to investigate the mechanical behaviors and the deformation process in B4C under complex stress conditions with six different biaxial perpendicular compression directions. The angle (θ) between one of the loading directions and the [0 0 0 1] c-axis ranged from 0° to 75° with every 15° interval. We found that the maximum stress at θ = 30° is 124.5 GPa, which is the lowest among six biaxial compressions. Simulation results show that the mechanism for amorphization in B4C under complex stress conditions is complicated. We take the θ = 30° biaxial compression as an example to explain the complicated deformation process. In the elastic deformation region, sudden bending of three-atom chains occurs and results in a stress fluctuation. Then the formation of new B–B bonds between the three-atom chains and the icosahedra leads to the first stress drop. After that, the B–C bonds in the chains are broken, resulting in the second stress drop. In this process, the icosahedra are partially destroyed. The stress increases continuously and then drops at the critical failure strain. Finally, the fully destruction of icosahedra leads to amorphization in B4C. However, under other five biaxial compressions, the B–C bonds in three-atom chains are not fractured before structural failure. Understanding the deformation mechanism for amorphization of B4C in real applications is prime important for proposing how to resist amorphization and enhance the toughness of B4C. read less A. Ektarawong, “Thermodynamic consideration and ground-state search of icosahedral boron subselenide B 12 (B 1 -x Se x ) 2 from a first-principles cluster expansion,” Physical Review B. 2018. link Times cited: 2 Abstract: The phase stability of icosahedral boron subselenide B12(B1−… read more Abstract: The phase stability of icosahedral boron subselenide B12(B1−xSex)2, where 0.5 x 1, is explored using a first-principles cluster expansion. The results shows that, instead of a continuous solid solution, B12(B1−xSex)2 is thermodynamically stable as an individual line compound at the composition of B9.5Se. The ground-state configuration of B9.5Se is represented by a mixture of B12(Se-Se), B12(B-Se), and B12(Se-B) with a ratio of 1:1:1, where they form a periodic ABCABC . . . stacking sequence of B12(Se-Se), B12(B-Se), and B12(Se-B) layers along the c axis of the hexagonal conventional unit cell. The structural and electronic properties of the ground-state B9.5Se are also derived and discussed. By comparing the derived ground-state properties of B9.5Se to the existing experimental data of boron subselenide B∼13Se, I proposed that the as-synthesized boron subselenide B∼13Se, as reported in the literature, has the actual composition of B9.5Se. read less X. Yang, W. Goddard, and Q. An, “Asymmetric twins in boron rich boron carbide.,” Physical chemistry chemical physics : PCCP. 2018. link Times cited: 2 Abstract: Twin boundaries (TBs) play an essential role in enhancing th… read more Abstract: Twin boundaries (TBs) play an essential role in enhancing the mechanical, electronic and transport properties of polycrystalline materials. However, the mechanisms are not well understood. In particular, we considered that they may play an important role in boron rich boron carbide (BvrBC), which exhibits promising properties such as low density, super hardness, high abrasion resistance, and excellent neutron absorption. Here, we apply first-principles-based simulations to identify the atomic structures of TBs in BvrBC and their roles for the inelastic response to applied stresses. In addition to symmetric TBs in BvrBC, we identified a new type of asymmetric twin that constitutes the phase boundaries between boron rich boron carbide (B13C2) and BvrBC (B14C). The predicted mechanical response of these asymmetric twins indicates a significant reduction of the ideal shear strength compared to single crystals B13C2 and B14C, suggesting that the asymmetric twins facilitate the disintegration of icosahedral clusters under applied stress, which in turn leads to amorphous band formation and brittle failure. These results provide a mechanistic basis towards understating the roles of TBs in BvrBC and related superhard ceramics. read less Q. C. Liu and X. M. Zhou, “Time-resolved light emission of a, c, and r-cut sapphires shock-compressed to 65 GPa,” Journal of Applied Physics. 2018. link Times cited: 2 Abstract: To investigate light emission and dynamic deformation behavi… read more Abstract: To investigate light emission and dynamic deformation behaviors, sapphire (single crystal Al2O3) samples with three crystallographic orientations (a, c, and r-cut) were shock-compressed by the planar impact method, with final stress ranges from 47 to 65 GPa. Emission radiance and velocity versus time profiles were simultaneously measured with a fast pyrometer and a Doppler pin system in each experiment. Wave profile results show anisotropic elastic-plastic transitions, which confirm the literature observations. Under final shock stress of about 52 GPa, lower emission intensity is observed in the r-cut sample, in agreement with the previous report in the literature. When final shock stress increases to 57 GPa and 65 GPa, spectral radiance histories of the r-cut show two stages of distinct features. In the first stage, the emission intensity of r-cut is lower than those of the other two, which agrees with the previous report in the literature. In the second stage, spectral radiance of r-cut increases with t... read less J. Knap and J. Clayton, “Continuum modeling of twinning, amorphization, and fracture: theory and numerical simulations,” Continuum Mechanics and Thermodynamics. 2018. link Times cited: 28 C. Kunka et al., “Nanotwinning and amorphization of boron suboxide,” Acta Materialia. 2018. link Times cited: 20 X. Yang, S. Coleman, J. LaSalvia, W. Goddard, and Q. An, “Shear-Induced Brittle Failure along Grain Boundaries in Boron Carbide.,” ACS applied materials & interfaces. 2018. link Times cited: 21 Abstract: The role that grain boundaries (GBs) can play on mechanical … read more Abstract: The role that grain boundaries (GBs) can play on mechanical properties has been studied extensively for metals and alloys. However, for covalent solids such as boron carbide (B4C), the role of GB on the inelastic response to applied stresses is not well established. We consider here the unusual ceramic, boron carbide (B4C), which is very hard and lightweight but exhibits brittle impact behavior. We used quantum mechanics (QM) simulations to examine the mechanical response in atomistic structures that model GBs in B4C under pure shear and also with biaxial shear deformation that mimics indentation stress conditions. We carried out these studies for two simple GB models including also the effect of adding Fe atoms (possible sintering aid and/or impurity) to the GB. We found that the critical shear stresses of these GB models are much lower than that for crystalline and twinned B4C. The two GB models lead to different interfacial energies. The higher interfacial energy at the GB only slightly decreases the critical shear stress but dramatically increases the critical failure strain. Doping the GB with Fe decreases the critical shear stress of at the boundary by 14% under pure shear deformation. In all GBs studied here, failure arises from deconstructing the icosahedra within the GB region under shear deformation. We find that Fe dopant interacts with icosahedra at the GB to facilitate this deconstruction of icosahedra. These results provide significant insight into designing polycrystalline B4C with improved strength and ductility. read less Y. You, K. Yoshida, T. Inoue, and T. Yano, “Helium bubbles and trace of lithium in B4C control rod pellets used in JOYO experimental fast reactor,” Journal of Nuclear Science and Technology. 2018. link Times cited: 7 Abstract: ABSTRACT B4C pellets used in the control rod of the experime… read more Abstract: ABSTRACT B4C pellets used in the control rod of the experimental fast reactor ‘JOYO’ with different 10B burnups from lower than 10 × 1020 captures/cm3 to 80 × 1020 captures/cm3 and irradiated at less than 800 °C were examined by transmission electron microscopy (TEM). In a B4C pellet irradiated in an irradiation capsule of ‘JOYO’ at 800 °C up to 30 × 1020 captures/cm3, intragranular helium bubbles appeared in flat plate-shapes with the plane of the plate parallel to the (111) rhombohedral plane. However, in the other specimens that were taken from an actual control rod, the helium gas formed very tiny spherical intergranular bubbles with a diameter of a few nanometers . These tiny bubbles make wavy arrays roughly parallel to the (111) plane. The B4C specimens were heated on a TEM in situ heating holder up to 1040 °C for 10 min. Clustering of tiny bubbles was observed, but did not extend to the plate-shaped bubbles. In high burnup specimens, large bubbles/cracks were rarely found along the {100} planes, which may correspond to the amorphous bands caused by the slip. While heating the specimens in TEM over 800 °C, liquid phases of lithium-bearing compoundsappeared on the surface of specimen. read less J. Clayton and J. Knap, “Continuum modeling of twinning, amorphization, and fracture: theory and numerical simulations,” Continuum Mechanics and Thermodynamics. 2017. link Times cited: 0 K. L. Joshi and S. Chaudhuri, “Observation of deflagration wave in energetic materials using reactive molecular dynamics,” Combustion and Flame. 2017. link Times cited: 17 K. Xie et al., “Microstructural characterization of boron-rich boron carbide,” Acta Materialia. 2017. link Times cited: 81 Q. An and W. Goddard, “Ductility in Crystalline Boron Subphosphide (B12P2) for Large Strain Indentation,” Journal of Physical Chemistry C. 2017. link Times cited: 14 Abstract: Our studies of brittle fracture in B4C showed that shear-ind… read more Abstract: Our studies of brittle fracture in B4C showed that shear-induced cracking of the (B11C) icosahedra leading to amorphous B4C regions induced cavitation and failure. This suggested that to obtain hard boron-rich phases that are ductile, we need to replace the CBC chains of B4C with two-atom chains that can migrate between icosahedra during shear without cracking the icosahedra. We report here a quantum mechanism (QM) simulation showing that under indentation stress conditions, superhard boron subphosphide (B12P2) displays such a unique deformation mechanism. Thus, stress accumulated as shear increases is released by slip of the icosahedra planes through breaking and then reforming the P–P chain bonds without fracturing the (B12) icosahedra. This icosahedral slip may facilitate formation of mobile dislocation and deformation twinning in B12P2 under high-stress conditions, leading to high ductility. However, the presence of twin boundaries (TBs) in B12P2 will weaken the icosahedra along TBs, leading to the fr... read less Q. An and W. Goddard, “Improved Ductility of B12 Icosahedra-based Superhard Materials through Icosahedral Slip,” Journal of Physical Chemistry C. 2017. link Times cited: 12 Abstract: Boron carbide (B4C) is superhard but suffers from brittle fa… read more Abstract: Boron carbide (B4C) is superhard but suffers from brittle failure because shear stress leads to the formation of amorphous shear bands in which the icosahedral clusters fracture, leading to amorphous regions with higher density than the crystal that results in tension-induced cavitation and brittle failure. On the basis of our previous studies of related systems, we speculated that replacing the C–B–C chains with Si2 and replacing cage C with Si might reduce or eliminate this amorphous shear band formation responsible for brittle failure. We consider (B10Si2)Si2, using density functional theory to examine its shear deformation. We find that the stress accumulated as shear increases is released by slip of the planes of icosahedra through breaking and then reforming the Si–Si chain bonds without fracturing (B10Si2) icosahedra. This is because the (B10Si2) icosahedra are more stable than the chain under highly stressed conditions. This chain disruption deformation mode prevents amorphous shear band formation... read less J. Clayton and J. Clayton, “Finsler-geometric continuum dynamics and shock compression,” International Journal of Fracture. 2017. link Times cited: 17 J. Li et al., “Ab initio study on the anisotropy of mechanical behavior and deformation mechanism for boron carbide,” Chinese Physics B. 2017. link Times cited: 11 Q. An and W. Goddard, “Nanotwins soften boron-rich boron carbide (B13C2),” Applied Physics Letters. 2017. link Times cited: 30 Abstract: Extensive studies of metals and alloys have observed that na… read more Abstract: Extensive studies of metals and alloys have observed that nanotwins lead to strengthening, but the role of nanotwins in ceramics is not well established. We compare here the shear strength and the deformation mechanism of nanotwinned boron-rich boron carbide (B_(13)C_2) with the perfect crystal under both pure shear and biaxial shear deformations. We find that the intrinsic shear strength of crystalline B_(13)C_2 is higher than that of crystalline boron carbide (B_4C). But nanotwins in B_(13)C_2 lower the strength, making it softer than crystalline B_4C. This reduction in strength of nanotwinned B_(13)C_2 arises from the interaction of the twin boundary with the C-B-C chains that connect the B_(12) icosahedra. read less P. Pokatashkin, P. Korotaev, and A. Yanilkin, “Amorphization in .ALPHA.-boron: A molecular dynamics study,” Physical Review B. 2017. link Times cited: 3 Q. An et al., “Superstrength through Nanotwinning.,” Nano letters. 2016. link Times cited: 60 Abstract: The theoretical strength of a material is the minimum stress… read more Abstract: The theoretical strength of a material is the minimum stress to deform or fracture the perfect single crystal material that has no defects. This theoretical strength is considered as an upper bound on the attainable strength for a real crystal. In contradiction to this expectation, we use quantum mechanics (QM) simulations to show that for the boron carbide (B4C) hard ceramic, this theoretical shear strength can be exceeded by 11% by imposing nanoscale twins. We also predict from QM that the indentation strength of nanotwinned B4C is 12% higher than that of the perfect crystal. Further, we validate this effect experimentally, showing that nanotwinned samples are harder by 2.3% than the twin-free counterpart of B4C. The origin of this strengthening mechanism is suppression of twin boundary (TB) slip within the nanotwins due to the directional nature of covalent bonds at the TB. read less S. Zhao et al., “Directional amorphization of boron carbide subjected to laser shock compression,” Proceedings of the National Academy of Sciences. 2016. link Times cited: 86 Abstract: Significance When crystalline solids are stressed quasi-stat… read more Abstract: Significance When crystalline solids are stressed quasi-statically, dislocation slip, twinning, and phase transformations are the predominant mechanisms to dissipate the imparted elastic energy. Under shock, high hydrostatic and shear stresses promptly build up at the shock front, favoring fast energy dissipation mechanisms. Amorphization, which may only involve localized atomic arrangements, is therefore an additional potential candidate. Shock-induced amorphization has now been reported in various materials and hence should be incorporated as a deformation/damage mechanism of crystals subjected to high-strain-rate loading. Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. Using high-power pulsed-laser-driven shock compression, unprecedented high strain rates can be achieved; here we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45∼50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. It is proposed that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversion calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B4C. read less J. Clayton, “Finsler-Geometric Continuum Mechanics and the Micromechanics of Fracture in Crystals.” 2016. link Times cited: 18 Abstract: A continuum theory for the mechanical response of solid bodi… read more Abstract: A continuum theory for the mechanical response of solid bodies subjected to potentially finite deformation is further developed and applied to solve several new problems in the context of the micromechanics of crystalline solids. The theory invokes concepts from Finsler differential geometry, and it provides a diffuse interface description of fracture surfaces. The director or internal state vector is associated with an order parameter describing degradation of the solid. Here, the deformation gradient between pseudo-Finsler reference and spatial configuration spaces is decomposed into a product of two terms, neither necessarily integrable to a vector field. The first is the recoverable elastic deformation, the second is the residual deformation attributed to changes in free volume in failure zones. The latter is restricted to spherical or isotropic symmetry; resulting Euler–Lagrange equations for mechanical and state variable equilibrium are derived. Metric tensors and volume elements depend on the internal state via a conformal transformation, i.e., Weyl scaling. This version of the theory is first applied to tensile fracture of magnesium. Analytical solutions demonstrate the model's capability to predict ductile versus brittle fracture depending on incorporation of Weyl scaling, with results aligned with molecular dynamics (MD) simulations. The second application is shear fracture in boron carbide: solutions depict weakening and tensile pressure in conjunction with structural collapse in shear transformation zones, as suggested by experiments, quantum mechanics, and/or MD simulations. read less C. Kunka, A. Awasthi, and G. Subhash, “Crystallographic and spectral equivalence of boron-carbide polymorphs,” Scripta Materialia. 2016. link Times cited: 19 Q. An, M. R. Kolan, H. Dong, M.-W. Chen, A. R. Oganov, and W. A. Goddard, “Nanotwinned Boron Suboxide (B6O): New Ground State of B6O.,” Nano letters. 2016. link Times cited: 42 Abstract: Nanotwinned structures in superhard ceramics rhombohedral bo… read more Abstract: Nanotwinned structures in superhard ceramics rhombohedral boron suboxide (R-B6O) have been examined using a combination of transmission electron microscopy (TEM) and quantum mechanics (QM). QM predicts negative relative energies to R-B6O for various twinned R-B6O (denoted as τ-B6O, 2τ-B6O, and 4τ-B6O), consistent with the recently predicted B6O structure with Cmcm space group (τ-B6O) which has an energy 1.1 meV/B6O lower than R-B6O. We report here TEM observations of this τ-B6O structure, confirming the QM predictions. QM studies under pure shear deformation and indentation conditions are used to determine the deformation mechanisms of the new τ-B6O phase which are compared to R-B6O and 2τ-B6O. The lowest stress slip system of τ-B6O is (010)/⟨001⟩ which transforms τ-B6O to R-B6O under pure shear deformation. However, under indentation conditions, the lowest stress slip system changes to (001)/⟨110⟩, leading to icosahedra disintegration and hence amorphous band formation. read less S. Coleman, E. Hernández-Rivera, K. Behler, J. Synowczynski-Dunn, and M. Tschopp, “Challenges of Engineering Grain Boundaries in Boron-Based Armor Ceramics,” JOM. 2016. link Times cited: 13 B. Tang, Q. An, and W. Goddard, “Improved Ductility of Boron Carbide by Microalloying with Boron Suboxide,” Journal of Physical Chemistry C. 2015. link Times cited: 26 Abstract: Boron carbide (B_4C) is the third hardest material in nature… read more Abstract: Boron carbide (B_4C) is the third hardest material in nature, but applications are hindered by its brittle failure under impact. We found that this brittle failure of B_4C arises from amorphous shear band formation due to deconstruction of icosahedral clusters, and on the basis of this model we suggest and validate with quantum mechanics (QM, PBE flavor of density function theory) that a laminated B_4C–B_6O composite structure will eliminate this brittle failure. Using QM to apply shear deformations along various slip systems, we find that the (001)/[100] slip system has the lowest maximum shear strength, indicating it to be the most plausible slip system. We find that this composite structure has a shear strength of 38.33 GPa, essentially the same as that of B_4C (38.97 GPa), indicating the same intrinsic hardness as B4C. However, the critical failure strain for (001)/[100] slip in the composite is 0.465, which is 41% higher than B_4C, indicating a dramatically improvement on ductility. This arises because incorporation of B_6O prevents the failure mechanism of B_4C in which the carbene formed during shear deformation reacts with the C–B–C chains. This suggests a new strategy for designing ductile superhard ceramics. read less J. Clayton, “Computational Modeling of Dual-Phase Ceramics withFinsler-Geometric Phase Field Mechanics,” Cmes-computer Modeling in Engineering & Sciences. 2019. link Times cited: 6 Abstract: A theory invoking concepts from differential geometry of gen… read more Abstract: A theory invoking concepts from differential geometry of generalized Finsler space in conjunction with diffuse interface modeling is described and implemented in finite element (FE) simulations of dual-phase polycrystalline ceramic microstructures. Order parameters accounting for fracture and other structural transformations, notably partial dislocation slip, twinning, or phase changes, are dimensionless entries of an internal state vector of generalized pseudo-Finsler space. Ceramics investigated in computations are a boron carbide-titanium diboride (B4C-TiB2) composite and a diamond-silicon carbide (C-SiC) composite. Deformation mechanisms-in addition to elasticity and cleavage fracture in grains of any phase-include restricted dislocation glide (TiB2 phase), deformation twinning (B4C and β-SiC phases), and stress-induced amorphization (B4C phase). The metric tensor of generalized Finsler space is scaled conformally according to dilatation induced by cavitation or other fracture modes and densification induced by phase changes. Simulations of pure shear consider various morphologies and lattice orientations. Effects of microstructure on overall strength of each composite are reported. In B4C-TiB2, minor improvements in shear strength and ductility are observed with an increase in the second phase from 10 to 18% by volume, suggesting that residual stresses or larger-scale crack inhibition may be responsible for toughness gains reported experimentally. In diamond-SiC, a composite consisting of diamond crystals encapsulated in a nano-crystalline SiC matrix shows improved strength and ductility relative to a two-phase composite with isolated bulk SiC grains. read less J. Clayton, “Fracture and Flow in Brittle Solids,” Shock Wave and High Pressure Phenomena. 2019. link Times cited: 0 J. Clayton, “Finsler-Geometric Modeling of Structural Changes in Solids,” Shock Wave and High Pressure Phenomena. 2019. link Times cited: 0 J. Clayton, R. B. Leavy, and J. Knap, “Mesoscale Modeling of Microcrystalline Ceramics,” International Conference on Computational & Experimental Engineering and Sciences. 2019. link Times cited: 0 Abstract: : Diffuse interface models and simulations capture deformati… read more Abstract: : Diffuse interface models and simulations capture deformation and failure of polycrystalline ceramics with multiple phases. Two heterogeneous ceramic solids are investigated. The first consists of a boron carbide matrix phase embedded with titanium diboride grains. The second consists of diamond crystals with a smaller fraction of silicon carbide grains, where the latter may encapsulate the former in a micro- or nano-crystalline matrix and/or may be interspersed as larger micro-crystals. A general constitutive framework suitable for representing behaviors of all phases of each material system is reported. This framework is implemented in three-dimensional (3D) finite element (FE) simulations of polycrystalline aggregates under compressive loading. Numerical results demonstrate effects of grain and phase morphology and activation or suppression of slip or twinning mechanisms on overall strength and ductility. read less Z. Zheng, T. Xu, D. Legut, and R. Zhang, “High-throughput informed machine learning models for ultrastrong B-N solids,” Computational Materials Science. 2022. link Times cited: 2 Q. Zeng, A. Tonge, and K. Ramesh, “A multi-mechanism constitutive model for the dynamic failure of quasi-brittle materials. Part II: Integrative model,” Journal of the Mechanics and Physics of Solids. 2019. link Times cited: 13 Q. Zeng, A. Tonge, and K. Ramesh, “A multi-mechanism constitutive model for the dynamic failure of quasi-brittle materials. Part I: Amorphization as a failure mode,” Journal of the Mechanics and Physics of Solids. 2019. link Times cited: 19 E. Hernández-Rivera, S. Chowdhury, S. Coleman, P. Ghassemi, and M. Tschopp, “Integrating exploratory data analytics into ReaxFF parameterization,” MRS Communications. 2018. link Times cited: 0 Abstract: We present a systematic approach to refine hyperdimensional … read more Abstract: We present a systematic approach to refine hyperdimensional interatomic potentials, which is showcased on the ReaxFF formulation. The objective of this research is to utilize the relationship between interatomic potential input variables and objective responses (e.g., cohesive energy) to identify and explore suitable parameterizations for the boron carbide (B–C) system. Through statistical data analytics, ReaxFF’s parametric complexity was overcome via dimensional reduction (55 parameters) while retaining enough degrees of freedom to capture most of the variability in responses. Two potentials were identified which improved on an existing parameterization for the objective set if interest, showcasing the framework’s capabilities. read less J. Lim, H. Kim, K. Cho, and M. Cho, “Fundamental mechanisms of fracture and its suppression in Ni-rich layered cathodes: Mechanics-based multiscale approaches,” Extreme Mechanics Letters. 2018. link Times cited: 16 J. D. Clayton and J. D. Clayton, “Generalized Finsler geometric continuum physics with applications in fracture and phase transformations,” Zeitschrift für angewandte Mathematik und Physik. 2017. link Times cited: 26 J. Clayton, “Generalized Finsler geometric continuum physics with applications in fracture and phase transformations,” Zeitschrift für angewandte Mathematik und Physik. 2016. link Times cited: 0 A. Rau, S. Jubin, J. R. Vella, and I. Kaganovich, “Simulations of graphite boronization: A molecular dynamics study of amorphization resulting from bombardment,” Frontiers of Physics. 2022. link Times cited: 0 Abstract: The molecular dynamics code LAMMPS was used to simulate the … read more Abstract: The molecular dynamics code LAMMPS was used to simulate the bombardment of a graphite structure by atomic boron with impact energies ranging from 50–250 eV. The transient structural evolution, penetration depth, and amorphous layer thickness were analyzed. Simulations show that larger impact energies lead to a greater volume of amorphization and penetration of boron, but that the growth rate of the amorphous layer decreases with increasing fluence. Furthermore, the change in surface chemistry of the amorphized structures was studied using the ReaxFF formalism, which found that the amorphization process introduces dangling bonds thus increasing reactivity in the amorphous region. read less S. Jubin, A. Rau, Y. Barsukov, S. Ethier, and I. Kaganovich, “Boron adatom adsorption on graphene: A case study in computational chemistry methods for surface interactions,” Frontiers of Physics. 2022. link Times cited: 4 Abstract: Though weak surface interactions and adsorption can play an … read more Abstract: Though weak surface interactions and adsorption can play an important role in plasma processing and materials science, they are not necessarily simple to model. A boron adatom adsorbed on a graphene sheet serves as a case study for how carefully one must select the correct technique from a toolbox of computational chemistry methods. Using a variety of molecular dynamics potentials and density functional theory functionals, we evaluate the adsorption energy, investigate barriers to adsorption and migration, calculate corresponding reaction rates, and show that a surprisingly high level of theory may be necessary to verify that the system is described correctly. read less D. Guo et al., “Grain Boundary Sliding and Amorphization are Responsible for the Reverse Hall-Petch Relation in Superhard Nanocrystalline Boron Carbide.,” Physical review letters. 2018. link Times cited: 58 Abstract: The recent observation of the reverse Hall-Petch relation in… read more Abstract: The recent observation of the reverse Hall-Petch relation in nanocrystalline ceramics offers a possible pathway to achieve enhanced ductility for traditional brittle ceramics via the nanosize effect, just as nanocrystalline metals and alloys. However, the underlying deformation mechanisms of nanocrystalline ceramics have not been well established. Here we combine reactive molecular dynamics (RMD) simulations and experimental transmission electron microscopy to determine the atomic level deformation mechanisms of nanocrystalline boron carbide (B_{4}C). We performed large-scale (up to ∼3 700 000 atoms) ReaxFF RMD simulations on finite shear deformation of three models of grain boundaries with grain sizes from 4.84 (135 050 atoms) to 14.64 nm (3 702 861 atoms). We found a reverse Hall-Petch relationship in nanocrystalline B_{4}C in which the deformation mechanism is dominated by the grain boundary (GB) sliding. This GB sliding leads to the amorphous band formation at predistorted icosahedral GB regions with initiation of cavitation within the amorphous bands. Our simulation results are validated by the experimental observations of an intergranular amorphous GB phase due to GBs sliding under indentation experiments. These theoretical and experimental results provide an atomistic explanation for the influence of GBs on the deformation behavior of nanocrystalline ceramics, explaining the reverse Hall-Petch relation. read less G. Subhash, A. Awasthi, C. Kunka, P. Jannotti, and M. Devries, “In search of amorphization-resistant boron carbide,” Scripta Materialia. 2016. link Times cited: 59 Q. An, K. Reddy, J. Qian, K. Hemker, M.-W. Chen, and W. G. III, “Nucleation of amorphous shear bands at nanotwins in boron suboxide,” Nature Communications. 2016. link Times cited: 37
Funding	Not available

Short KIM ID The unique KIM identifier code.	SM_389039364091_000
Extended KIM ID The long form of the KIM ID including a human readable prefix (100 characters max), two underscores, and the Short KIM ID. Extended KIM IDs can only contain alpha-numeric characters (letters and digits) and underscores and must begin with a letter.	Sim_LAMMPS_ReaxFF_AnGoddard_2015_BC__SM_389039364091_000
DOI	10.25950/d253fc36 https://doi.org/10.25950/d253fc36 https://commons.datacite.org/doi.org/10.25950/d253fc36
KIM Item Type	Simulator Model
KIM API Version	2.2
Simulator Name The name of the simulator as defined in kimspec.edn.	LAMMPS
Potential Type	reax
Simulator Potential	reaxff
Run Compatibility	portable-models

Verification Check Dashboard

(Click here to learn more about Verification Checks)

Grade	Name	Category	Brief Description	Full Results	Aux File(s)
P All elements claimed by model are supported in at least one of the tested configurations.	vc-species-supported-as-stated	mandatory	The model supports all species it claims to support; see full description.	Results	Files
P Periodic boundary conditions were correctly supported for all configurations that the model was able to compute.	vc-periodicity-support	mandatory	Periodic boundary conditions are handled correctly; see full description.	Results	Files
F Model energy does NOT have permutation symmetry for at least one configuration that the model was able to compute. This indicates an error in the implementation of the model.	vc-permutation-symmetry	mandatory	Total energy and forces are unchanged when swapping atoms of the same species; see full description.	Results	Files
D The letter grade D was assigned because the normalized error in the computation was 4.18088e-03 compared with a machine precision of 2.22045e-16. The letter grade was based on 'score=log10(error/eps)', with ranges A=[0, 7.5], B=(7.5, 10.0], C=(10.0, 12.5], D=(12.5, 15.0), F>15.0. 'A' is the best grade, and 'F' indicates failure.	vc-forces-numerical-derivative	consistency	Forces computed by the model agree with numerical derivatives of the energy; see full description.	Results	Files
F The model is C^0 continuous. This means that the model has continuous energy, but a discontinuous first derivative.	vc-dimer-continuity-c1	informational	The energy versus separation relation of a pair of atoms is C1 continuous (i.e. the function and its first derivative are continuous); see full description.	Results	Files
P Model energy and forces are invariant with respect to rigid-body motion (translation and rotation) for all configurations the model was able to compute.	vc-objectivity	informational	Total energy is unchanged and forces transform correctly under rigid-body translation and rotation; see full description.	Results	Files
P Model energy has inversion symmetry for all configurations the model was able to compute.	vc-inversion-symmetry	informational	Total energy is unchanged and forces change sign when inverting a configuration through the origin; see full description.	Results	Files
F Memory leak detected.	vc-memory-leak	informational	The model code does not have memory leaks (i.e. it releases all allocated memory at the end); see full description.	Results	Files
N/A Thread safety can only be checked for KIM Models.	vc-thread-safe	mandatory	The model returns the same energy and forces when computed in serial and when using parallel threads for a set of configurations. Note that this is not a guarantee of thread safety; see full description.	Results	Files

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

Species: C

Cohesive Energy Graph

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

Species: C

Diamond Lattice Constant

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

Species: C

Dislocation Core Energies

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

(No matching species)

FCC Elastic Constants

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

Species: C

FCC Lattice Constant

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

Species: C

FCC Stacking Fault Energies

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

(No matching species)

FCC Surface Energies

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

(No matching species)

SC Lattice Constant

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

Species: C

Cubic Crystal Basic Properties Table

Species: B

Species: C

Tests

CohesiveEnergyVsLatticeConstant__TD_554653289799_003

Cohesive energy versus lattice constant curve for monoatomic cubic lattices v003

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

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

Test	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Cohesive energy versus lattice constant curve for bcc C v004	view	37473
Cohesive energy versus lattice constant curve for diamond C v004	view	40092
Cohesive energy versus lattice constant curve for fcc C v004	view	26128
Cohesive energy versus lattice constant curve for sc C v004	view	5540

ElasticConstantsCubic__TD_011862047401_006

Elastic constants for cubic crystals at zero temperature and pressure v006

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

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

Test	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Elastic constants for diamond C at zero temperature v001	view	2989434
Elastic constants for fcc C at zero temperature v006	view	107339
Elastic constants for sc C at zero temperature v006	view	32688

EquilibriumCrystalStructure__TD_457028483760_002

Equilibrium structure and energy for a crystal structure at zero temperature and pressure v002

Creators:
Contributor: ilia
Publication Year: 2024
DOI: https://doi.org/10.25950/2f2c4ad3

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

Test	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype A13B2_hR15_166_a2h_c v002	view	284175
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype A4B_hR15_166_2h_ac v002	view	832721
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_cF16_227_c v002	view	260837
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_cF240_202_h2i v002	view	2892662
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_cF8_227_a v002	view	111981
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_cI16_206_c v002	view	127216
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_cI16_229_f v002	view	85975
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_cI8_214_a v002	view	5492605
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_cP20_221_gj v002	view	155413
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hP12_194_e2f v002	view	68233
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hP16_194_e3f v002	view	164763
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hP2_191_c v002	view	2138327
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hP4_194_f v002	view	62401
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hP8_194_ef v002	view	16012017
Equilibrium crystal structure and energy for B in AFLOW crystal prototype A_hR105_166_ac9h4i v002	view	1589846
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hR10_166_5c v002	view	456889
Equilibrium crystal structure and energy for B in AFLOW crystal prototype A_hR12_166_2h v002	view	122249
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hR14_166_7c v002	view	331955
Equilibrium crystal structure and energy for B in AFLOW crystal prototype A_hR15_166_ac2h v002	view	297299
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hR4_166_2c v002	view	254064
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hR60_166_2h4i v002	view	902590
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_mC16_12_4i v002	view	168885
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_oC16_65_mn v002	view	489650
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_oC16_65_pq v002	view	98917
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_oC8_65_gh v002	view	73277
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_oI120_71_lmn6o v002	view	4059214
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_oP16_62_4c v002	view	178824
Equilibrium crystal structure and energy for B in AFLOW crystal prototype A_oP28_58_3g2h v002	view	398729
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_tI8_139_h v002	view	88345
Equilibrium crystal structure and energy for B in AFLOW crystal prototype A_tP48_134_2m2n v002	view	161500
Equilibrium crystal structure and energy for B in AFLOW crystal prototype A_tP50_134_a2m2n v002	view	1345930
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype AB5_aP12_2_i_5i v002	view	570412
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype AB5_hP6_156_a_a2b2c v002	view	146799
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype AB5_oI12_44_a_b2c v002	view	78745
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype AB7_cP8_215_a_ce v002	view	70603
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype AB7_hP8_156_b_4ab2c v002	view	198138
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype AB7_hR8_160_a_7a v002	view	139930
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype AB7_oP8_25_a_bcdef v002	view	74735
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype AB7_tP8_115_b_ce2g v002	view	53104

LatticeConstant2DHexagonalEnergy__TD_034540307932_002

Cohesive energy and equilibrium lattice constant of hexagonal 2D crystalline layers v002

Creators: Ilia Nikiforov
Contributor: ilia
Publication Year: 2019
DOI: https://doi.org/10.25950/dd36239b

Given atomic species and structure type (graphene-like, 2H, or 1T) of a 2D hexagonal monolayer crystal, as well as an initial guess at the lattice spacing, this Test Driver calculates the equilibrium lattice spacing and cohesive energy using Polak-Ribiere conjugate gradient minimization in LAMMPS

Test	Test Results	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Cohesive energy and equilibrium lattice constant of graphene v002		view	1104

LatticeConstantCubicEnergy__TD_475411767977_007

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

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

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

Test	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Equilibrium zero-temperature lattice constant for bcc C v007	view	26724
Equilibrium zero-temperature lattice constant for diamond C v007	view	88418
Equilibrium zero-temperature lattice constant for fcc C v007	view	41080
Equilibrium zero-temperature lattice constant for sc C v007	view	13676

LatticeConstantHexagonalEnergy__TD_942334626465_005

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

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

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

Test	Test Results	Link to Test Results page	Benchmark time Usertime multiplied by the Whetstone Benchmark. This number can be used (approximately) to compare the performance of different models independently of the architecture on which the test was run. Measured in Millions of Whetstone Instructions (MWI)
Equilibrium lattice constants for hcp B v005		view	432512
Equilibrium lattice constants for hcp C v005		view	797678

Errors

ElasticConstantsCubic__TD_011862047401_006

Test	Error Categories	Link to Error page
Elastic constants for bcc C at zero temperature v006	other	view

ElasticConstantsHexagonal__TD_612503193866_004

Test	Error Categories	Link to Error page
Elastic constants for hcp B at zero temperature v004	other	view
Elastic constants for hcp C at zero temperature v004	other	view

EquilibriumCrystalStructure__TD_457028483760_000

Test	Error Categories	Link to Error page
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_cF240_202_h2i v000	other	view
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hP2_191_c v000	other	view
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype AB7_tP8_115_b_ce2g v000	other	view

EquilibriumCrystalStructure__TD_457028483760_002

Test	Error Categories	Link to Error page
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_cP1_221_a v002	other	view
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hP12_194_bc2f v002	other	view
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hP4_194_bc v002	other	view
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_hR2_166_c v002	other	view
Equilibrium crystal structure and energy for C in AFLOW crystal prototype A_oC8_67_m v002	other	view
Equilibrium crystal structure and energy for BC in AFLOW crystal prototype AB5_tI24_141_a_b2e v002	other	view

LatticeConstantCubicEnergy__TD_475411767977_007

Test	Error Categories	Link to Error page
Equilibrium zero-temperature lattice constant for bcc B v007	other	view
Equilibrium zero-temperature lattice constant for diamond B v007	other	view
Equilibrium zero-temperature lattice constant for fcc B v007	other	view
Equilibrium zero-temperature lattice constant for sc B v007	other	view

LinearThermalExpansionCoeffCubic__TD_522633393614_001

Test	Error Categories	Link to Error page
Linear thermal expansion coefficient of diamond C at 293.15 K under a pressure of 0 MPa v001	other	view

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Sim_LAMMPS_ReaxFF_AnGoddard_2015_BC__SM_389039364091_000

Verification Check Dashboard

Visualizers (in-page)

BCC Lattice Constant

Cohesive Energy Graph

Diamond Lattice Constant

Dislocation Core Energies

FCC Elastic Constants

FCC Lattice Constant

FCC Stacking Fault Energies

FCC Surface Energies

SC Lattice Constant

Cubic Crystal Basic Properties Table

Tests

Errors

Files

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