Effects of lattice strain and ion displacement on the bonding mechanism of the ferroelectric perovskite material BaTiO3: first-principles study

The effects of lattice strain and ion displacement on the bonding mechanism of the perovskite material BaTiO3 have been studied by using the density-functional theory within the full-potential linear augmented plane wave (FP-LAPW) method. The valence and the bonding charge density, the density of states (DOS), the local DOS and the partial DOS were calculated to investigate the bonding mechanisms. The charge transfer, along with the bonding process, was analysed by using the atoms in molecules theory (AIM). Based on the analysis of the bonding and the topological characteristics, the evolution of the bonding strength according to different lattice strains and ion displacements along with the phase transition of BaTiO3 is shown quantitatively. Moreover, the evolution of the spontaneous polarization of BaTiO3 corresponding to the ion displacements is also discussed by a modern theory of polarization in the present paper