BiFeO_3结构性质与相转变的第一性原理研究

采用基于密度泛函理论的第一性原理计算,系统地研究了BiFeO3的7种不同空间群(R3c,R3m,P4mm,Cm,Pm3m,R3m和R3c)结构及其转变关系.结果表明,铁电相R3c结构是基态,不同结构之间也存在着一定的转变关系,其变化主要包括两种形式,在111]方向上Bi3+相对FeO6八面体存在一定的位移和FeO6八面体绕111]极化轴的反铁扭曲旋转.此外,还得出BiFeO3的薄膜结构受到衬底结构的作用会导致其从三方相(R3c)向四方相(P4mm)转变.

First-principles investigation on the phase transitions of BiFeO3

Using the first-principles method based on density functional theory, we investigate the structural properties of seven different phases of BiFeO₃ including R3c, R3m, P4mm, Cm, Pm3 m, R3 m and R3 c and structural transition. The results show that the ground state has the R3c phase, and that phase transitions can occur among these phases, which may be characterized by two types of structural transitions. One is the relative displacement between octahedral FeO₆ and Bi³⁺, and the other is the rotation of octahedral FeO₆ along the 111] axis. Furthermore, the BiFeO₃ film is found to be able to change from R3c phase to P4mm phase, owing to the substrate effect.