Theoretical investigation on BaTiO3 with periodic density functional theory BLYP method

The electronic structures and bonding modes of BaTiO3 in the cubic and the distorted tetragonal structures have been investigated with periodic DFT-BLYP method. The results show that Ti displacement makes the charge transfer from O atoms to Ba and Ti atoms. Ba atoms might play a more important role in distributing the transferred charges than one has imagined. Our results also indicate that Ti displacement enhances the Ti-O and Ba-O(2) bonds. Only Ba-O(1) is slightly weakened. The pi bonding interaction of 3d(xz)(Ti)-2p(x)[O(1)] and 3d(yz)(Ti)-2p(y)[O(1)] favors the tetragonal phase whereas the a bond 4p(z)(Ti)-2p(z)[O(1)] favors the paraelectric cubic phase. Our results are consistent with the vibronic theory that the ferroelectric instability of BaTiO3 is due to the formation of new covalency by distortion. (C) 2001 Elsevier Science B.V. All rights reserved.