Fig. 1. Supercell geometry and the doped position of the anatase TiO₂. The unit of the bond lengths is angstrom.

Fig. 2. Total density of states of undoped and S-doped anatase TiO₂. The vertical dotted line indicates the position of the E_F.

Fig. 3. Projected density of states (PDOS) of S-doped anatase TiO₂. The vertical dotted line indicates the position of the E_F.

Fig. 4. The two-dimensional profile of the electron density at the (010) plane of undoped TiO₂ (a) and S-doped anatase TiO₂ (b).

Fig. 5. Optical absorption curves of undoped and S-doped TiO₂. Schematic illustrations of the band structure of undoped and S-doped anatase TiO₂ were indicated at the insets. Energies are not in scale. E_g, E_{g_S}, and , represent the band gap of TiO₂, S-doped TiO₂, and the band gap narrowing of S-doped TiO₂, respectively.