Quantum Monte Carlo calculations of the formation energy ES of Schottky defects in MgO were reported which demonstrated the feasibility of using this approach to overcome the deficiencies of density functional theory. In order to investigate system-size errors, density functional theory calculations were also made of ES in repeating cells of up to 1000 atoms. These indicated that quantum Monte Carlo calculations of systems of only 54 atoms should yield high precision. The density functional theory calculations also provided the relaxed structures used in the variational and diffusion Monte Carlo calculations. For MgO, ES was found to be in close agreement with results of density functional theory and model interaction potentials, and was consistent with experimental values.

Schottky Defect Formation Energy in MgO Calculated by Diffusion Monte Carlo. D.Alfè, M.J.Gillan: Physical Review B, 2005, 71[22], 220101 (3pp)