First-Principles Calculations of the Electronic Structure of Imperfect Crystals in the Coherent Potential Approximation

The results of electronic structure calculations of imperfect crystals—nonstoichiometric metal oxides (TiO_{2 – x}, TiO_{1 – x}, Al₂O_{3 – x}) are reviewed. All calculations were performed within the density functional theory in the coherent potential approximation with vacancies randomly distributed in metal and oxygen sublattices. It is found that the deviations from stoichiometric composition are accompanied by appearance of vacancy induced electronic states inside the band gap of initial insulating oxides.