Oxygen Vacancies of Anatase(101): Extreme Sensitivity to the Density Functional Theory Method

We present a systematic investigation of the influence of theoretical parameters on the characterization of surface and subsurface oxygen vacancies in anatase with the 101 facet exposed. This metastable phase of titania continues to resist a facile description of its defects, particularly, in the reduced state. Nine nonequivalent sites were examined under varying levels of theory with characterization of formation energies, geometry, and electronic states extracted from Bader charges, charge density, and density of states. At DFT+U levels of theory, these sites remain nonequivalent. We note a new surface oxygen vacancy minimum related to localization of electrons at surface and a subsurface Ti atoms, rather than the more favorable localization at neighboring surface Ti atoms.