First-Principles Molecular Dynamics Calculations of the Equation of State for Tantalum

Shigeaki Ono

doi:10.3390/ijms10104342

Abstract

The equation of state of tantalum (Ta) has been investigated to 100 GPa and 3,000 K using the first-principles molecular dynamics method. A large volume dependence of the thermal pressure of Ta was revealed from the analysis of our data. A significant temperature dependence of the calculated effective Grüneisen parameters was confirmed at high pressures. This indicates that the conventional approach to analyze thermal properties using the Mie-Grüneisen approximation is likely to have a significant uncertainty in determining the equation of state for Ta, and that an intrinsic anharmonicity should be considered to analyze the equation of state.

Highlights

Equations of state (EOS) for some elemental metals have been used as an internal pressure gauge inX-ray diffraction high-pressure studies using diamond anvil cell [e.g., 1–3] or multi-anvil press experiments [e.g., 4–6]
We have investigated the EOS of Ta, which has a body-centred cubic structure, using the first-principles molecular dynamics method
We used the high-pressure experimental data to determine the compressibility at room temperature, and used the generalized gradient approximation (GGA) and the projector augmented-wave method (PAW) in simulations to calculate the thermal pressure

Summary

Introduction

Equations of state (EOS) for some elemental metals have been used as an internal pressure gauge inX-ray diffraction high-pressure studies using diamond anvil cell [e.g., 1–3] or multi-anvil press experiments [e.g., 4–6]. We noticed that the scatter of the experimental bulk modulus values at room temperature was much smaller than that obtained from first-principles calculations [7,9,12,13,14,15,16,17]. This indicates that experiments are more accurate than first-principles calculations for determining the bulk modulus at room temperatures. The first-principles molecular dynamics calculations have significant advantages to investigate the physical properties of materials at high temperatures

Methods

Results

Conclusion