Electronic structures and optical properties of rutile TiO2 with different point defects from DFTÂ +Â U calculations

The electronic states and formation energies of four types of lattice point defects in rutile TiO2 are studied using the first-principles calculations. The existence of oxygen vacancy leads to a deep donor defect level in the forbidden band, while the Ti interstitial forms two local states. It is predicted that oxygen vacancy prefers to combine with Ti-interstitial to form VO-Tii dimer by a partial 3d electron transfer from the Tii to its neighboring VO. The charge distribution between a Ti interstitial and its neighboring Ti ions partially shields the Coulomb interactions. Lastly, optical properties of these defective lattices are discussed.