<i>Ab initio</i>based empirical potential used to study the mechanical properties of molybdenum

Park, Hyoungki; Fellinger, Michael R.; Lenosky, Thomas J.; Tipton, William W.; Trinkle, Dallas R.; Rudin, Sven P.; Woodward, C.; Wilkins, John W.; Hennig, Richard G.

doi:10.1103/physrevb.85.214121

Cited by 77 publications

(73 citation statements)

References 69 publications

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“…Lenosky et al 25 first parametrized the MEAM formalism through the use of cubic splines for the study of defects in Si. The use of splines for parameterizing empirical potentials increases model flexibility and efficiency, and has been successfully applied to the study of martensitic transformations in pure titanium 28 , shock-loading in niobium 29,31 and dislocation dynamics in molybdenum 30 . SW potentials, initially developed for the modeling of cubic-diamond Si, have been successfully applied to amorphous Si 32 as well as Ge 33 and other systems.…”

Section: A Empirical Extension Of the Meam Potentialmentioning

confidence: 99%

Ab initio based empirical potential applied to tungsten at high pressure

et al. 2017

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Density-functional theory forces, stresses and energies comprise a database from which the optimal parameters of a spline-based empirical potential combining Stillinger-Weber and modified embeddedatom forms are determined. Accuracy of the potential is demonstrated by calculations of ideal shear, stacking fault, vacancy migration, elastic constants and phonons all between 0 and 100 GPa. Consistency with existing models and experiments is demonstrated by predictions of screw dislocation core structure and deformation twinning in a tungsten nanorod. Lastly, the potential is used to study the stabilization of fcc tungsten at high pressure.

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Section: A Empirical Extension Of the Meam Potentialmentioning

confidence: 99%

Ab initio based empirical potential applied to tungsten at high pressure

et al. 2017

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“…Another possible consideration in this regard is the use of genetic algorithms or similar techniques to generate additional candidate structures. In the case of Mo, for example, the use of genetic algorithms recently uncovered several complex structures with T = 0 energies much closer to that of bcc than is the case for the fcc, hcp or hex-ω structures [48].…”

Section: B Z-methods Melt Curves For Small and Large Cellsmentioning

confidence: 99%

Polymorphism and melt in high-pressure tantalum

2012

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Recent small-cell (< 150-atom) quantum molecular dynamics (QMD) simulations for Ta based on density functional theory (DFT) have predicted a hexagonal omega (hex-ω) phase more stable than the normal bcc phase at high temperature (T) and pressure (P) above 70 GPa [Burakovsky et al., Phys. Rev. Lett. 104, 255702 (2010)]. Here we examine possible high-T , P polymorphism in Ta with complementary DFT-based model generalized pseudopotential theory (MGPT) multi-ion interatomic potentials, which allow accurate treatment of much larger system sizes (up to ~ 80000 atoms). We focus on candidate bcc, A15, fcc, hcp, and hex-ω phases for the high-T , P phase diagram to 420 GPa, studying the mechanical and relative thermodynamic stability of these phases for both small and large computational cells. Our MGPT potentials fully capture the T = 0 DFT energetics of these phases, while MGPT-MD simulations demonstrate that the higher-energy fcc, hcp and hex-ω structures are only mechanically stabilized at high temperature by large, size-dependent, anharmonic vibrational effects, with the stability of the hex-ω phase also being found to be a sensitive function of its c / a ratio. Both twophase and Z-method melting techniques have been used in MGPT-MD simulations to determine relative phase stability and its size dependence. In the large-cell limit, the twophase method yields accurate equilibrium melt curves for all five phases, with bcc producing the highest melt temperatures at all pressures and hence being the most stable phase of those considered. The two-phase bcc melt curve is also in good agreement with dynamic experimental data as well as with the MGPT melt curve calculated from bcc and 2 liquid free energies. In contrast, we find that the Z method produces only an upper bound to the equilibrium melt curve in the large-cell limit. For the bcc and hex-ω structures, however, this is a close upper bound within 5% of the two-phase results, although for the A15, fcc, and hcp structures, the Z-melt curves are 25-35% higher in temperature than the two-phase results. Nonetheless, the Z method has allowed us to study melt size effects in detail. We find these effects to be either small or modest for the cubic bcc, A15, and fcc structures, but to have a large impact on the hexagonal hcp and hex-ω melt curves, which are dramatically pushed above that of bcc for simulation cells less than 150 atoms. The melt size effects are driven by and closely correlated with similar size effects on the mechanical stability and the vibrational anharmonicity. We further show that for the same simulation cell sizes and choice of c / a ratio, the MGPT-MD bcc and hex-ω melt curves are in good agreement with the QMD results, so the QMD prediction is confirmed in the small-cell limit. But in the large-cell limit, the MGPT-MD hex-ω melt curve is always lowered below that of bcc for any choice of c / a , so bcc is the most stable phase.We conclude that for the non-bcc Ta phases studied, one requires simulation cells of at least 250-500 atoms to be free ...

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“…We assumed a = 3.167Å for the lattice constant, based on the equilibrium value for T = 0 K in the s-MEAM description [22]. The dimensions of the block were taken to be L x = 100 √ 3 a, L y = 8 √ 6 a, and L z = 124 √ 2 a.…”

Section: Computational Set-upmentioning

confidence: 99%

“…The potential developed in 2012 by Park et al [22] offers a very good description of a number of properties of molybdenum, including structural (lattice constants, energetics of stable and metastable phases), elastic (elastic constants, phonon dispersion curves), and thermodynamic properties (coefficients of thermal expansion, compressibility). Moreover, the properties of defected Mo are also well described, both for point and line defects, with the latter of particular interest in studies of plasticity [30].…”

Section: Introductionmentioning

confidence: 99%

“…At the same time its predictions for elastic constants, phonon frequencies, surface energies and defect formation energies are in very good agreement with results obtained at the density functional theory (DFT) level of theory. With the successes of [11,22,31,32] in mind, we anticipate an increase in the number of available parameterisations of s-MEAM in the near future.…”

Section: Introductionmentioning

confidence: 99%

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Central-force decomposition of spline-based modified embedded atom method potential

Winczewski

Dziedzic

2016

Modelling Simul. Mater. Sci. Eng.

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Abstract. Central-force decompositions are fundamental to the calculation of stress fields in atomic systems by means of Hardy stress. We derive expressions for a central-force decomposition of the spline-based modified embedded atom method (s-MEAM) potential. The expressions are subsequently simplified to a form that can be readily used in molecular-dynamics simulations, enabling the calculation of the spatial distribution of stress in systems treated with this novel class of empirical potentials. We briefly discuss the properties of the obtained decomposition and highlight further computational techniques that can be expected to benefit from the results of this work. To demonstrate the practicability of the derived expressions, we apply them to calculate stress fields due to an edge dislocation in bcc Mo, comparing their predictions to those of linear elasticity theory.

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Ab initiobased empirical potential used to study the mechanical properties of molybdenum

Cited by 77 publications

References 69 publications

Ab initio based empirical potential applied to tungsten at high pressure

Ab initio based empirical potential applied to tungsten at high pressure

Polymorphism and melt in high-pressure tantalum

Central-force decomposition of spline-based modified embedded atom method potential

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