Formation of oxygen vacancies on the TiO2(1Â 1Â 0) surfaces

Density functional theory was employed to investigate the formation and properties of the oxygen vacancies on the rutile TiO2(1 1 0) surface. It is found that the formation of the positively charged bridging-oxygen vacancy (BOV+, 4.2 eV) is the most favored one, followed by the positively charged in-plane-oxygen vacancy (POV+, 4.5 eV). In contrast, the formation of the neutral bridging-oxygen and in-plane-oxygen vacancies (BOV and POV), and their dication oxygen vacancies (BOV2+ and POV2+) needs much higher energies (7.9 and 8.3 vs. 8.1 and 8.6 eV), respectively.