Molecular dynamics of MgSiO3 perovskite at high pressures: Equation of state, structure, and melting transition

The objective of this study was to develop a micromechanical approach for determining the Mie–Grüneisen EOS parameters of iron under the Hugoniot states. The multiscale shock technique (MSST) coupled with molecular dynamics (MD) simulations was employed to describe the shocked Hugoniot relation of single-crystal (SC) and nanocrystalline (NC) iron under high pressures. The Mie–Grüneisen equation of state (EOS) parameters, the cold pressure (Pc), the cold energy (Ec), the Grüneisen coefficient (γ), and the melting temperature (Tm) are discussed. The error between SC and NC iron results was found to be less than 1.5%. Interestingly, the differences in Hugoniot state (PH) and the internal energy between SC and NC iron were insignificant, which shows that the effect of grain size (GS) under high pressures was not significant. The Pc and Ec of SC and NC iron calculated based on the Morse potential were almost the same with those calculated based on the Born–Mayer potential; however, those calculated based on the Born–Mayer potential were a little larger at high pressures. In addition, several empirical and theoretical models were compared for the calculation of γ and Tm. The Mie–Grüneisen EOSs were shown on the 3D contour space; the pressure obtained with the Hugoniot curves as the reference was larger than that obtained with the cold curves as the reference.

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Pressure dependence of the Grüneisen parameter and melting temperature of some metals

International Journal of Modern Physics B ◽

10.1142/s0217979221502556 ◽

2021 ◽

pp. 2150255

Author(s):

K. Sunil ◽

D. Ashwini ◽

Vijay S. Sharma

Keyword(s):

Experimental Data ◽

Molecular Dynamics ◽

Equation Of State ◽

Pressure Dependence ◽

High Pressures ◽

Grüneisen Parameter ◽

Thermal Equation ◽

Gruneisen Parameter ◽

Melting Temperatures ◽

Volume Dependence

We have used a method for determining volume dependence of the Grüneisen parameter in the Lindemann law to study the pressure dependence of melting temperatures in case of 10 metals viz. Cu, Mg, Pb, Al, In, Cd, Zn, Au, Ag and Mn. The reciprocal gamma relationship has been used to estimate the values of Grüneisen parameters at different volumes. The results for melting temperatures of metals at high pressures obtained in this study using the Lindemann law of melting are compared with the available experimental data and also with the values calculated from the instability model based on a thermal equation of state. The analytical model used in this study is much simpler than the accurate DFT calculations and molecular dynamics.

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Elasticity, Thermal Properties, and Molecular Dynamics Using Non-Empirical Tight-Binding

MRS Proceedings ◽

10.1557/proc-491-501 ◽

1997 ◽

Vol 491 ◽

Author(s):

Ronald E. Cohen ◽

Lars Stixrude ◽

Evgeny Wasserman

Keyword(s):

Molecular Dynamics ◽

Thermal Properties ◽

Equation Of State ◽

Total Energy ◽

High Pressures ◽

Tight Binding ◽

Rare Gases ◽

Thermal Equation ◽

Wide Range ◽

A Cell

ABSTRACTWe have further developed and applied a new non-empirical tight-binding total energy model to properties of Si, Xe, and Fe at high pressures. We have studied elasticity of various phases of each of these, demonstrating that the new model is applicable to a wide range of materials, including semiconductors, rare gases, and transition metals. We have used the particle-in-a-cell method to study the thermal equation of state of hep Fe and find excellent agreement with the shock equation of state. A molecular dynamics code has been developed based on this method, and we have studied the properties of Fe liquid at high pressures.

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