Optical properties of N and transition metal R (R=V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) codoped anatase TiO2

The electronic structures, deformation charge density, dipole moment and optical properties of N and transition metal R (R=V, Cr, Mn, Fe, Co, Ni, Cu and Zn) codoped anatase TiO2 are studied using the plane-wave ultrasoft pseudopotential method of density functional theory (DFT). The results exhibit that the absorption coefficients of the N+Cr-doped TiO2 are in accordance with the experimental values in the visible-light region. The calculated results reveal that the N+R-doped TiO2 is helpful for enhancing the absorption coefficient in the visible-light region; especially, among the eight materials, N+Mn-doped TiO2 has the largest value of absorption coefficient in the visible-light region. The ionic bonding and Jahn-Teller distortion would contribute to increase the photocatalytic activity of TiO2 in the visible-light region. All in all, for doped TiO2, the large dipole moment of TiO6 octahedron can enhance the optical responses in the visible-light region; in this work, however, it is found that the small dipole moment of TiO6 octahedron would increase the absorption coefficient in the visible-light region.