Modification of Local Electronic Structures Due to Phase Transition in Perovskite-Type Oxides, SrBO₃ (B=Zr, Ru, Hf)

Abstract

The local electronic structures are simulated for a perovskite-type oxide with four polymorphous phases, SrZrO₃, using the DV-Xα molecular orbital method. It is found that a series of phase transitions occurs at certain temperatures so as to retain not only the Zr-O bond strength, but also the Sr-O bond strength, by the tilting of ZrO₆ octahedra and the attendant accommodation to the Zr-O and the Sr-O interionic distances. The occurrence of such smart phase transitions is observed in other perovskite-type oxides, SrRuO₃ and SrHfO₃. Another type of phase transition occurs by the cooperative ionic displacements along the [100] direction in BaTiO₃. The differences in the local chemical bond are discussed between the two types of phase transitions.