Neutral defects in SrTiO₃ studied with screened hybrid density functional theory

The properties of neutral defects in SrTiO₃ are calculated using the screened hybrid density functional of Heyd, Scuseria, and Ernzerhof. The formation energies, the crystal field splittings affecting the SrTiO₃ band structure, and the relaxation geometries around each defect are discussed. Oxygen vacancies introduced in SrTiO₃ are found to cause a small tetragonal elongation of the lattice along the z-axis. The resulting conduction band minimum electron effective masses deviate from the bulk values and support the proposal of enhanced electron mobility along the direction of the compressive strain. The locations of the various defect bands within the SrTiO₃ gap are estimated without introducing any post hoc corrections, thus allowing a more reliable comparison with experiment.