First-principle study of the electronic structure and optical property of Nb-doped anatase TiO2

The absorption edge shifted to long wavelength direction and short wavelength direction of two opposite experimental conclusions have been reported, when the band-gap and absorption spectra of Nb-doped anatase TiO2 were studied. In order to solve this contradiction, the electronic structure and the optical property of Nb heavy doped anatase TiO2 have been studied by the first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory with +U method modification. The calculated results indicate that the higher the Nb-doping is, the higher the total energy is, the worse the stability is, the higher the formation energy is, the more difficult the doping is, the wider the optical band-gap is, the more obvious the absorption edge shifting to short wavelength direction is, the lower the absorptivity and the reflectivity is, which is in agreement with the experimental results. The reasonable interpretation of the contradiction has been reported in this paper, too.