The electronic properties of an oxygen vacancy at ZrO₂- terminated (001) surfaces of a cubic PbZrO₃: Computer simulations from the first principles

Combining B3PW hybrid exchange-correlation functional within the density functional theory (DFT) and a supercell model, we calculated from the first principles the electronic structure of both ideal PbZrO₃ (001) surface (with ZrO₂- and PbO-terminations) and a neutral oxygen vacancy also called the F center. The atomic relaxation and electronic density redistributions are discussed. Thermodynamic analysis of pure surfaces indicates that ZrO₂ termination is energetically more favorable than PbO-termination. The O vacancy on the ZrO₂-surface attracts ≈0.3 e (0.7 e in the bulk PbZrO₃), while the remaining electron density from the missing O^2- ion is localized mostly on atoms nearest to a vacancy. The calculated defect formation energy is smaller than in the bulk which should lead to the vacancy segregation to the surface. Unlike Ti-based perovskites, the vacancy-induced (deep) energy level lies in PbZrO₃ in the middle of the band gap.