First principle calculations of electronic, band structural, and optical properties of BixSr1-xTiO3 perovskite

Based on the first-principles plane-wave ultrasoft pseudopotential method, we set up models of perovskite-type oxides BixSr1-xTiO3 (x = 0, 0.25, 0.5, 0.625, 1), and the geomertry optimization, the electronic and band structure were studied. The calculation results show that the binding energy decreases in Bi Sri. TiO3 after Sr2+ replaced by Bi3+. The calculations of the band structure show that BixBa1-xTiO3 are direct band gap semiconductors. The partial substitution of Bi3+ ions can increase the band gap and the absorption spectra ranges shift blue, and the values of band gaps are in the order of Bi0.625Sr0.375TiO3 > Bi0.5Sr0.5TiO3 > Bi0.25Sr0.73TiO3 > SrTiO3 > BiTiO3, and the absorption spectrum becomes wider in the order of Bi0.625Sr0.375TiO3 > BiTiO3 > Bi0.5Sr0.5TiO3 > Bi0.25Sr0.75TiO3 > SrTiO3. Based on the density of states, the top of the valence band is hybridized by O-2p and Sr-5s and the bottom of the conduction band state is mainly constituted by the Ti-3d states and Bi-6p states. The regulation of photo-catalytic activity of the perovskite SrTiO3 can be realized by Bi ions substituting for Sr ions, and Bi-based perovskite BiTiO3 will be a potential photocatalytic material.