Theoretical prediction on the structural, electronic, and polarization properties of tetragonal Bi₂ZnTiO₆

Abstract

We present first-principles investigations on the structural, electronic, and polarization properties of Bi₂ZnTiO₆ using density-functional theory within the generalized gradient approximation. The theoretical structure we obtained confirms the extra large tetragonality observed by experiment. The materials exhibit a semiconductor behavior with an indirect band gap determined by the occupied O 2p and unoccupied Bi 6p states. There are strong hybridization effects between Bi–O ions, as well as Ti–O and Zn–O ones. The resulting covalent bondings, having a PbTiO₃-type two-dimensional character, strengthen each other and favor the coupling between the tetragonal distortion of unit cell and the off-center displacement of A and B-site cations and O anions due to the existence of Zn, and result in the large tetragonality of this compound. Berry-phase calculation gives the polarization as high as 122 μC/cm².