Electronic Structure and Visible-Light Absorption of Transition Metals (TM=Cr, Mn, Fe, Co) and Zn-Codoped SrTiO_3: a First-Principles Study

First-principles calculations are performed on the influence of transition metal (TM=Cr, Mn, Fe, Co) as codopants on the electronic structure and visible-light absorption of Zn-doped SrTiO_3. The calculated results show that (Zn,Mn)-codoped SrTiO_3 requires the smallest formation energy in four codoping systems. The structures of the codoped systems display obvious lattice distortion, inducing a phase transition from cubic to rhombohedral after codoping. Some impurity Cr, Mn and Co 3d states appear below the bottom of conduction band and some Fe 3d states are located above the top of valence band, which leads to a significant narrowing of band gap after transition metal codoping. The enhancement of visible-light absorption are observed in transition metals (TM=Cr, Mn, Fe, Co) and Zn codoped SrTiO_3 systems. The prediction calculations suggested that the (Zn,Mn)- and (Zn,Co)-codoped SrTiO_3 could be the desirable visible-light photocatalysts.