Vacancy and defect structures in metal oxides

The self-consistent local density (LD) theory is used to model vacancy and defect structures in metal oxides by use of the embedded cluster scheme. LCAO-MO expansions of cluster orbitals are obtained by the DV-Xα discrete variational method, and used to characterize energy levels, charge distributions, X-ray absorption and cohesive energies. Examples are drawn from recent work on transition metal monoxides such as Fe_1-xO, ceramic materials such as yttrium-stabilized zirconia, and the alumina/ruby system. It is shown that in addition to predicting spectroscopic properties, LD theory has now reached a stage of implementation where lattice stability and local site geometry can be usefully explored.