Electron spin localisation and correlation effects for point defects in semi-ionic solids

Point defects strongly influence the electrical, catalytic and optical properties of important industrial materials such as silica, aluminosilicates and aluminophosphates. We concentrate here on the predictive ability of modern ab initio solid-state tools to describe electron localised states in these materials. We apply a periodic boundary conditions approach to investigate equilibrium configurations and electronic structures of oxygen vacancies in the form of diamagnetic V-o and paramagnetic E' centres. Localisation of the electronic states at the defect is studied using both Hartree-Fock (HF) and Density Functional theories. Thus, we are able to characterise the effect of electron correlation on spill polarisation and electron trapping. Geometries and energetics of defect formation are investigated, along with the one-electron spectra and spin/charge density distributions, which allow us to gather a comprehensive representation of the defect ground state. (C) 2000 Elsevier Science B.V. All rights reserved.