A comparison of defect energies in MgO using Mott-Littleton and quantum mechanical procedures

The authors compare the predictions of Mott-Littleton calculations, based on empirical interatomic potentials, with predictions based on self-consistent solutions of the Schrodinger equation for embedded clusters. Simple vacancy and substitutional defects in MgO are modelled using both the classical Mott-Littleton and quantum mechanical methods. Particular attention is paid to the size of the quantum mechanical cluster, the different ways that polarisation is taken into account and the choice of basis set. Results are presented for closed-shell systems only, namely V" Mg and V o vacancies and for Li' Mg , Na' Mg , Al Mg , F o and Cl o substitutional impurities. They find a respectable level of agreement between the quite distinct approaches. This both validates the classical calculations and indicates useful generalisations combining the two approaches.