PRESSURE-VOLUME-TEMPERATURE EQUATIONS OF STATE: A COMPARATIVE STUDY BASED ON NUMERICAL SIMULATIONS

Abstract

The P-V-T equation of state (EoS) models of Birch-Murnaghan, Vinet and Poirier-Tarantola have been compared with one another and discussed in the light of their ability to reproduce thermoelastic functions and parameters by means of fitting to pressure-volume-temperature data artificially generated for spinel, corundum and forsterite. Numerical simulations relying upon semi-empirical potentials, lattice dynamics and the quasiharmonic approximation have been used to generate P-V-T data. The results obtained indicate that all the P-V-T EoSs tested predict bulk modulus at ambient conditions with errors confined, at worst, within a few percent, and reproduce correctly its dependence on temperature. The derivatives of the bulk modulus versus P and PT are less satisfactorily modelled. The bulk thermal expansion is determined by EoSs within a few percent error, but the deviations increase significantly if the approximation of linear dependence of EoS on temperature is used (linearised thermal pressure model).