Equations of state of MgO, Au, Pt, NaCl-B1, and NaCl-B2: Internally consistent high-temperature pressure scales

Abstract

Semiempirical equations of state (EoS) of Au, Pt, MgO, NaCl-B1, and NaCl-B2 based on expanded Mie–Grüneisen–Debye approach, which are consistent both with the Mie–Grüneisen–Bose–Einstein approach and the thermochemical, X-ray, ultrasonic and shock-wave data in a wide pressure-temperature range, have been constructed. It is shown that to determine the volume dependence of the Grüneisen parameter, not only shock-wave and static compression data, but also experimental information on heat capacity, bulk moduli, volume, and thermal expansion coefficient at zero pressure need to be taken into account. Intrinsic anharmonicity is of great importance at construction of EoS at high temperatures and x=V/V ₀>1. Cross-comparison of the current equations of state with independent measurements shows that these EoS may be used as the internally consistent and independent pressure scales in a wide range of temperatures and pressures.

Keywords:

• Expanded Mie-Grüneisen-Debye EoS
• Pressure scales
• Grüneisen parameter
• Intrinsic anharmonicity
• Gold
• Platinum
• Magnesium oxide
• Sodium chloride

Acknowledgements

The authors thank Artem Oganov (ETH, Zurich, Switzerland) as the first reader of this manuscript and Kenichi Takemura (NIMS, Tsukuba, Japan) for sharing raw x-ray diffraction data. P.D. thanks A.D., who took the liberty of presentation of part of this work for COMPRES workshop in Geophysical Laboratory in January 2007. This work was supported by the Russian Foundation for Basic Research, grants No. 05-05-64491 and No. 08-08-00147.