Effects of Pressure on Diffusion and Vacancy Formation in MgO from Nonempirical Free-Energy Integrations

The free energies of vacancy pair formation and migration in MgO were computed via molecular dynamics using free-energy integrations and a nonempirical ionic model with no adjustable parameters. The intrinsic diffusion constant for MgO was obtained at pressures from 0 to 140GPa and temperatures from 1000 to 5000K. Excellent agreement was found with the zero pressure diffusion data within experimental error. The homologous temperature model which relates diffusion to the melting curve describes well our high pressure results within our theoretical framework. {copyright} {ital 1997} {ital The American Physical Society}