On the origin of supertetragonality in BaTiO3
Abstract
Understanding ferroelectricity is of both fundamental and technological importance to further stimulate the development of new materials designs and manipulations. Here, we perform an in-depth first-principle study on the well-known ferroelectric barium titanate BaTiO3 under a hydrostatic negative pressure, showing an isosymmetric phase transition to a supertetragonal phase with high c/a ratio of 1.3. The microscopic origin and driving mechanisms of this phase transition are identified as a drastic change of the covalently π-bonded electrons. These findings provide guidance in the search for new supertetragonal phases, with great opportunities for novel multiferroic materials; and can be generalized in the understanding of other isosymmetric phase transitions.