Electronic and optical properties of Cr and Cr-N doped anatase TiO2 from screened Coulomb hybrid calculations.

We studied the electronic and atomic structures of anatase TiO2 codoped with Cr and N using hybrid density functional theory calculations. The nonlocal screened Hartree-Fock exchange energy is partially mixed with the traditional semilocal exchange energy. This not only patches the bandgap underestimation but also improves the description of the anion/cation-driven impurity states and the magnetization of the dopants. Cr and/or N doping modifies the valence and conduction band edges of TiO2, leading to significant bandgap reduction. Hence, Cr, N and Cr-N doped TiO2 are promising for enhanced visible light absorbance.