Fig. 1.

Oxygen-atom vacancy on rutile TiO₂(110) surface. The PBE approximation to the energy functional predicts a delocalized electronic state with energy at the bottom of the conduction band, whereas the self-interaction–corrected PBE-SIC/2 functional predicts a localized state with energy in the gap, 0.9 eV below the conduction band edge, in good agreement with experiment (28). The self-interaction correction lowers the energy of the valence states and brings the estimated band gap into agreement with experiments (Table 2).