Electronic and structural properties of BaTiO3: A proposal about the role of Ti 3s and 3p states for ferroelectricity

Abstract We have investigated the role of the Coulomb repulsions between Ti 3s and 3p states and O 2s and 2p states in ferroelectric BaTiO 3 , using a first-principles calculation with optimized structures. It has been found that the Coulomb repulsions between Ti 3s and 3p x ( y ) states and O x ( y ) 2s and 2p x ( y ) states are closely related to the appearance of Ti ion displacement in tetragonal BaTiO 3 . The mechanism of the Ti–O Coulomb repulsions also seems to be consistent with the appearance of Ti ion displacement in rhombohedral BaTiO 3 . Our investigation suggests that the Coulomb repulsions between Ti 3s and 3p x ( y ) states and O x ( y ) 2s and 2p x ( y ) states have an important role in the appearance of the ferroelectric state in tetragonal BaTiO 3 .