Atomic and electronic structure of perfect and defective PbZrO₃ perovskite: Hybrid DFT calculations of cubic and orthorhombic phases

The structural and electronic properties of pure cubic and low-temperature orthorhombic PbZrO₃ (antiferroelectric phase), as well as cubic PbZrO₃ containing single F-centers (neutral oxygen vacancies) have been simulated by means of ab initio hybrid density functional calculations. We observed a substantial increase of the Pb-O bond covalency in ideal orthorhombic PbZrO₃ with respect to its cubic phase. Relatively large displacement of four Pb atoms nearest to the F-center (0.25 Å towards the defect) could affect the PbZrO₃ ferroelectric properties. An O vacancy in the bulk PbZrO₃ attracts ≈0.7 e, and the remaining electron density from the missing O^2- is localized mostly on four nearest Pb atoms. This leads to appearance of an energy level in the middle of the band gap of cubic PbZrO₃, unlike the shallow F-level found in SrTiO₃.