Vacancy defects in strontium titanate: Ab initio calculation

A full-potential linearized-augmented plane-wave calculation was used to study structural and electronic properties of defected SrTiO3 with two concentrations of oxygen vacancies. These properties were found to remarkably depend on the oxygen vacancy concentration. The defect states associated with oxygen vacancies are identified within the energy gap. The ground state properties, equilibrium lattice constants, bulk moduli, the formation energy, densities of electron states, band structures and charge density are determined and discussed for this compound. It is found that an oxygen vacancy creates more localized in-gap states. With increasing oxygen deficiency, the electrons left behind by oxygen removal not only localize on Sr (Ti) 3d orbitals but also on the vacancy sites. Model structures of 2 × 2 × n (n = 1, 2, 3 and 4) supercells are used.