Self-consistent ab initio total energy calculations were performed for (110) surfaces at which the atomic structure had been relaxed to equilibrium. It was found that, in the case of stoichiometric super-cells, there were no surface states in the band gap; in agreement with experimental observations. The presence of O vacancies on the surface gave rise to Ti 3d-like surface states at the edge of the bulk conduction band. The relaxations of the atoms at the surface were found to be large, and those which were produced by a vacancy were localized in its vicinity. It was noted that bulk vacancies introduced states which were located at about 0.3eV below the edge of the bulk conduction band.

Defects on TiO2 (110) Surfaces. Ramamoorthy, M., King-Smith, R.D., Vanderbilt, D.: Physical Review B, 1994, 49[11], 7709-15