Electronic structure and optical properties of anion-doped monoclinic NaTaO3 by first-principles calculations

First-principles density function theory calculations have been performed on the electronic structure and optical properties of mono-doped and co-doped monoclinic NaTaO3 systems. Doping of certain nonmetal ions (N, C, S, and P) and certain co-dopant pairs (C-N, S-N, P-N, and S-P) is investigated. Our calculations show that substitutional doping of C at a Na site, N at an O site, S at a Na site, and P at a Ta site require smaller formation energy based on the optimized structures of doped NaTaO3. In the case of mono-doped NaTaO3, the results indicate that the band gaps were all narrowed resulting in redshift of the absorption edge. However, for C-N, S-N, P-N, and S-P co-doped systems, though the band gap broadened, the appearance of mid-gap and movement of conduction band minimum (CBM) to Fermi energy led to absorption in the visible range. On the basis of the calculated results on nonmetal doped NaTaO3, we theoretically predicted that mono-doped NaTaO3 is more suitable for photocatalysts of water splitting.