The high-temperature and high-pressure behavior of MgO derived from lattice vibration calculations. Kieffer's model revisited

Abstract

The model of Kieffer has been extended and applied to derive thermodynamic properties from the lattice vibrational behavior of pure substances. The model for MgO has been validated in the pressure range between 0 and 300 GPa and temperature range between 100 and 4000 K. The model is constrained by thermodynamic data, lattice vibrational frequencies and data on transverse and longitudinal sound velocities. It is shown that intrinsic anharmonicity is present in the different modes of vibration. It is concluded that the accuracy of the results is not significantly affected by using different equations of state for the principal isotherm. It is shown that all thermodynamic data and sound wave velocity data are accurately described except for shock-wave data. The model of Kieffer is contrasted with the Mie–Grüneisen–Debye model and it is shown that the former represents more accurately experimental thermodynamic and longitudinal and transverse sound wave velocity data.