Abstract
We calculate the electronic structure and optical properties of F-doped anatase TiO2. The results indicate that the band gap of F-doped TiO2 increases slightly compared with the pure TiO2. However, it is interesting that the visible absorption of F-doped TiO2 located between 600 and 700 nm is observed, and it enhances gradually with the increasing F concentration. Furthermore, according to the results of densities of states and imaginary part of dielectric function ∊2(ω), we propose that the transition between Ti 3d and Ti 3d states may be responsible for the visible absorption, but not the band gap narrowing.