ABO3型晶体中氧的电子自发极化

计算O^-2在晶体场中出现的Jahn-Teller效应,得到具有电矩的2p_π3s3d₀杂化原子轨道。BO₆八面体共价性质决定了ABO₃晶体的各种极化相。理论给出P_s比值、钛位移大小和热力学参数ξ′,ζ′均接近于实验结果。统一解释了钛酸钡的三个相转变。相变条件给出七种晶体中氧的屏蔽常数平均值与Slater的值一致。

ELECTRONIC SPONTANEOUS POLARIZATION OF O-2 IN THE ABO3-TYPE CRYSTALS

The crystal fields lower the 3s3d₀ electronic energy level of O^-2 and make it hybrid with the 2p_π level at transition temperature to give a spontaneous polarization orbit according to the Jahn-Teller effect. In various polarized phases, the direction of each polarization orbit of three oxygens in unit cell was determined by the covalent bonds of BO₆ octahedron. A correct ratio of the componeons of P_s in four phases of BaTiO₃, and the screen constant which agrees with Slater's value for O^-2 were given. For cubic to tetragonal transition, the theory was compared with Devonshire's theory.