Comparative study of the structural and thermodynamic properties of MgO at high pressures and high temperatures

Shell model molecular dynamics (MD) method is used to predict the structure and thermodynamic properties of MgO at high temperatures and high pressures using the Stoneham–Sangster and Lewis–Catlow potentials, respectively. In order to account for the observed large departures from the Cauchy relation of the elastic constants of the MgO, the breathing shell model (BSM) is also introduced in MD simulation, in which the repulsive radii of oxygen ions are allowed to deform isotropically under the effects of other ions in the crystal. The properties including the expansivity, constant-pressure heat capacity, isothermal bulk modulus are calculated in a wide range of temperatures (300–3000 K) and pressures (0–150 GPa). The obtained structural and thermodynamic parameters are compared with the available experimental data and other theoretical results. Compared with Stoneham–Sangster and Lewis–Catlow potentials, the MD simulation with BSM is very successful in reproducing accurately the measured volumes of MgO and the results are more compressible. Meanwhile, some thermodynamic parameters have been predicted at elevated temperatures and high pressures. The detailed knowledge of thermodynamic behavior of the major Earth-forming mineral—periclase (MgO) at extreme P–T conditions are of fundamental importance to our understanding of the Earth's lower mantle and the history of the Earth's formation.