摘要
Structural parameters and electronic band gaps of dense TiO 2 polymorphs, i.e., α-PbO 2 , baddeleyite, fluorite, and cotunnite types of structures, were calculated using a first-principles density functional method with local-density approximation. The ambient phases, i.e., rutile and anatase, with known theoretical and experimental data were used to ensure the validity of the calculations. The fluorite-type TiO 2 turned out to have the narrowest band gap, 1.08 or 2.18 eV after applying a very approximate band gap correction, due to highly symmetrical TiO 8 polyhedra with Ti 3d and O 2p orbitals in the most mixed state. Ti with eight coordinated oxygens, as feasible under high pressure or residual stress, may have potential applications as a visible-light-responsive photocatalyst. © 2005 American Chemical Society.