Electronic and Structural Properties of ABO3: Role of the B-O Coulomb Repulsions for Ferroelectricity.

Kaoru Miura,Masaki Azuma,Hiroshi Funakubo

doi:10.3390/ma4010260

Abstract

We have investigated the role of the Ti–O Coulomb repulsions in the appearance of the ferroelectric state in BaTiO as well as the role of the Zn–O Coulomb repulsions in BiZnTiO, using a first-principles calculation with optimized structures. In tetragonal BaTiO, it is found that the Coulomb repulsions between Ti 3s and 3p states and O 2s and 2p states have an important role for the appearance of Ti ion displacement. In BiZnTiO, on the other hand, the stronger Zn–O Coulomb repulsions, which are due to the 3s, 3p, and 3d (d) states of the Zn ion, have more important role than the Ti–O Coulomb repulsions for the appearance of the tetragonal structure. Our suggestion is consistent with the other ferroelectric perovskite oxides O in the appearance of tetragonal structures as well as rhombohedral structures.

Highlights

We discuss the role of Ti 3s and 3p states for ferroelectricity for ferroelectricity in tetragonal BaTiO3
Using a first-principles calculation with optimized structures, we have investigated the role of the Coulomb repulsions between Ti 3s and 3p states and O 2s and 2p states in ferroelectric BaTiO3
It has been found that the Coulomb repulsions between Ti 3s and 3px (y) states and Ox (y) 2s and 2px (y) states are closely related to the appearance of Ti ion displacement in tetragonal BaTiO3

Summary

Introduction

Since Cohen [1,2] proposed an origin for ferroelectricity in perovskite oxides, investigations of ferroelectric materials using first-principles calculations have been extensively studied [3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]. BaTiO3 is a well-known ferroelectric ABO3 , and shows the tetragonal structure at room temperature Even in this well-known material, the optimized structure by the PP methods of first-principles calculations is strongly dependent on the choice of the Ti PPs, i.e., preparation for Ti 3s and 3p semicore states in addition to Ti 3d and 4s valence states is essential to the appearance of the tetragonal structure. Wang et al [10] reported the first-principles calculational results of BZT They emphasized the importance of the strong Bi–O hybridization as well as the Ti–O and Zn–O ones for the appearance of the tetragonal structure with high c/a ratio. We investigated the roles of the Ti–O and Zn–O Coulomb repulsions in the appearance of a ferroelectric states in tetragonal BaTiO3 [17] and BZT [18] by the analysis of a first-principles PP method. We discuss a general role of B–O Coulomb repulsions for ferroelectricity in tetragonal ABO3 based on our previous reports [17,18]

Calculations

BaTiO3 : Role of Ti 3s and 3p states for ferroelectricity

Summary