2004 年 45 巻 7 号 p. 2056-2061
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.
