Range-separated hybrid exchange-correlation functional analyses of anatase TiO2 doped with W, N, S, W/N, or W/S
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The electronic properties and atomic structures of W, N, S, W/N, and W/S dopings of anatase TiO2 have been systematically investigated using the density functional theory. The exchange and correlation effects have been treated with the Heyd, Scuseria, and Ernzerhof (HSE) hybrid functional. Mixing traditional semilocal and nonlocal screened Hartree-Fock exchange energies, the HSE method corrects the band gap and also improves the description of anion/cation-derived gap states. Enhanced charge-carrier dynamics, observed for W/N codoped titania, can partly be explained by mutually passivating modifications of N 2p and W 5d states on its electronic structure. Following this trend, we have found an apparent band gap narrowing of 1.03 eV for W/S codoping. This is due to the large dispersion of S 3p states at the valance band top extending its edge to higher energies and Ti-S-W hybridization appearing at the bottom of the conduction band. W/S-TiO2 might show a strong visible-light response comparable to W/N codoped anatase catalysts.