Native point defects in anatase were investigated by using first-principles pseudopotential calculations based upon density-functional theory. Antisite defects, namely, Ti-antisite (TiO) and O-antisite (OTi), had high formation energies and were hence unstable. In contrast, all other fundamental native defects (Tii, Oi, VTi, and VO) had low formation energies. In particular, the Ti interstitial (Tii) was a quadruple donor defect with lowest formation energy in p-type samples, whereas Ti vacancy (VTi) was a quadruple acceptor defect with lowest formation energy in n-type samples. Interstitial oxygen (Oi) would spontaneously and strongly bind to lattice O, resulting in a neutral O2 dimer substituting on one O site. None of the four low-energy defects had energy levels inside the density-functional theory band-gap.

First-Principles Study of Native Defects in Anatase TiO2. Na-Phattalung, S., Smith, M.F., Kim, K., Du, M.H., Wei, S.H., Zhang, S.B., Limpijumnong, S.: Physical Review B, 2006, 73[12], 125205