High-pressure lattice dynamics and thermoelasticity of MgO

We present an ab initio study of the thermoelastic properties of MgO over a wide range of pressure and temperature. Phonon dispersions for equilibrium and strained configurations are obtained from density-functional perturbat ion theory. They are used to calculate thermodynamical potentials within th e quasiharmonic approximation and several derived quantities of physical in terest without further approximations. These include the temperature depend ence of individual elastic constants at high pressures. Extensive and succe ssful comparisons with experimental data demonstrate that the quasiharmonic approximation combined with ab initio phonon calculations provides an impo rtant theoretical approach for exploring thermodynamical properties of mate rials over a considerable pressure-temperature regime.