Electronic structure ofTiO2:Ru

We present ab initio electronic structure calculations of Ru-doped ${\mathrm{TiO}}_{2}$ using a supercell geometry. Our results show three Ru-induced defect states occurring within the fundamental ${\mathrm{TiO}}_{2}$ band gap with a center of mass \ensuremath{\sim}1 eV above the O 2p manifold in agreement with absorption and photoelectrochemical experiments. These midgap states were found to be localized on the Ru atoms with ${\mathit{t}}_{2\mathit{g}\mathrm{\ensuremath{-}}}$like symmetry.