Modeling the thermodynamic and elastic properties of MgO crystals at Earth’s mantle conditions using statistical moment method

Abstract

The thermodynamic and elastic properties of MgO crystals with B1 structure are comprehensively studied by statistical moment method in this manuscript. We derive physically explicit analytical expressions for thermodynamic quantities such as molar volume, isothermal compressibility, thermal expansion coefficient, isochoric and isobaric heat capacities, elastic moduli such as Young’s modulus, bulk compressibility moduli, shear modulus and elastic wave velocities. The $P$–$V$–$T$ relationship for MgO crystals calculated by us up to 365 GPa and 3000 K is consistent with previous experimental and theoretical findings. From this, we construct a reliable equation of state as a pressure scale for studying coating materials. We found that the addition of the Morse potential to the Born–Mayer–Higgins (BMH) interaction potential allows for more accurate reproduction of the thermodynamic and elastic properties of B1 structured MgO crystals at Earth’s mantle conditions. Anharmonic effects have a marked influence on the thermodynamic properties of MgO crystals in the temperature region greater than 1000 K. The anharmonic effects of the lattice vibrations increase the fracture resistance and reduce the wave propagation of MgO crystals at Earth’s mantle conditions.