Modified electron-gas study of the stability, elastic properties, and high-pressure behavior of MgO and CaO crystals

Abstract

A theoretical study of the crystal structure and bonding in the simple inorganic oxide crystals magnesium oxide and calcium oxide is reported. An a priori method based on an electron-gas approximation is applied to an ionic description of these crystals. The quantities calculated are the equilibrium interionic separation, the elastic constants and their pressure derivatives, the transition pressures and volume changes in high-pressure-induced phase transitions, and the thermodynamic stability of the crystal structures. Comparison with available experimental data shows good agreement, without any adjustable parameters in the theory. We conclude that the ionic description of these crystals is rather accurate for energy calculations, provided that a suitably stabilized oxide ion is used in the theory.