Embedded cluster models for electronic structure and energetics of complex oxides

Electronic structures and energetics of complex oxide systems have been investigated using the self-consistent embedded cluster model in the framework of local density theory. Ground state charge and spin distributions and energy level diagrams are generated for perfect host lattices, and for vacancy and impurity environments. The polarization response of perfect and defect lattices is explored by performing self-consistent calculations in the presence of an external electric field. Electron density difference maps are used to display local changes in electron distributions induced by vacancies, cation substitution, and external electric fields. Local multipolar moments are determined for quantitative analysis of the response of the system to the induced disturbances. Cohesive energies are calculated for molecular fragments, and are used to study relative energetics of the perfect host lattices and various defect structures with and without external electric field. Results obtained from oxide systems with NaCl-type structure, as well as rare-earth and alkali-earth stabilized cubic zirconia and superconducting La ₂ CuO ₄ , will be presented and discussed.