The quasi-particle electronic structure of charged oxygen vacancies in TiO2

Abstract

We studied the quasi-particle electronic structure of oxygen vacancies V O in rutile TiO2 using G0W0 approximation on top of GGA + U as a method of choice. In order to determine the degree of electronic localization, we examined the combined G0W0@GGA + U scheme in which both G0W0 and GGA + U methods are individually one step toward a better inclusion of the non-locality of the exchange-correlation potential. Our G0W0@GGA + U results realize the weak nature of electron correlation. Moreover, it was shown that the U-dependency of the energy gap in the perfect bulk is slightly stronger than that of a defected sample while the U-dependence of V O induced levels in different charged states show different behaviors. Eventually, we concluded that applying G0W0@GGA + U, though it does not stabilize oxygen vacancy levels in the gap, however, it does correct the formation energies and transition levels more closely to the experimental measurements.