Analysis of isothermal equations of state for ionic solids and geophysical minerals at high temperatures

We present an analysis of various isothermal equations of state (EOSs) such as the Birch - Murnaghan EOS, the Vinet EOS, the Shanker EOS, and the logarithmic EOS by Studying the pressure-volume relationships, the isothermal bulk modulus K, and its first pressure derivative K-T' for ionic solids such as NaCl, KCl, MgO,CaO and geophysical minerals such as T MgSiO3 perovskite at temperatures ranging from room temperature up to their melting temperatures under high compressions down to V/V-0 = 0.6 where V-0 is the volume V at P = 0. T-he results are compared with the corresponding values derived from the Hama-Suito EOS based on the augmented-plane-wave (APW) method and the quantum statistical model (QSM). The comparison reveals that the Vinet EOS and the Shanker EOS yield the closest agreement with the ab-initio results. At higher temperatures and higher compressions the values of P. K, and K-T' obtained from the Birch-Murnaghan EOS are somewhat higher and those obtained from the logarithmic EOS are lower than the values obtained from the Hama-Suito EOS. The results obtained in the present study compare well with the available experimental P- V- T data for MgO and MgSiO3.