Electronic structures of V-doped anatase TiO2

First-principles calculations using the full-potential linearized augmented plane-wave method have been performed to investigate the electronic structure of V-doped TiO2 in the anatase modification. In calculations with local density approximation (LDA), V 3d states are located at the bottom of the conduction band of the TiO2 host. The V-doped TiO2 was shown to be a half-metal. However, in calculations with LDA+U (Hubbard coefficient) approach that incorporates strongly correlated interactions of both Ti and V 3d electrons, the band gap of TiO2 host was obtained as 3.18 eV, very close to the experimental result of 3.2 eV. Additionally, spin-polarized V 3d states were obtained which are gap states located in the band gap of TiO2 host. The V-doped TiO2 was indicated to be an insulator. An analysis of the V 3d orbital splitting in a D2d local symmetry of the TiO2 host indicates that the LDA+U approach presents a more accurate description on the electronic structure of V-doped TiO2 than the standard LDA approach. In addition, the energy of V-doped TiO2 in the ferromagnetic phase was calculated with LDA+U to be 0.034 eV lower than that in the anti-ferromagnetic phase. This energy difference corresponds to 400 K, close to the Curie temperature, ∼405 K in V-doped TiO2.