Electronic structure of TiO2 rutile with oxygen vacancies: Ab initio simulations and comparison with the experiment

The electronic structure of TiO2 rutile with oxygen vacancies, which is a promising insulator, has been analyzed. The ab initio density functional calculations, as well as the comparative analysis of the results obtained in the sigma-GGA spin-polarized generalized approximation and those obtained by the sigma-GGA + U method with allowance for Coulomb correlations of d electrons titanium atoms in the Hartree-Fock approximation for the Hubbard model, have been performed. It has been found that the effective electron mass in rutile is anisotropic and there are both light (m (e) (*) = (0.6-0.8)m (0), where m (0) is the free-electron mass) and heavy (m (e) (*) > 1m (0)) electrons, whereas holes in rutile are only heavy (m (e) (*) a (c) 3/4 2m (0)). It has been shown that the sigma-GGA + U method gives a deep occupied level in the band gap and that an oxygen vacancy in rutile is an electron and hole trap.