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.
@article{arxiv.2201.07569,
title = {On the origin of supertetragonality in BaTiO$_3$},
author = {Simon Mellaerts and Jin Won Seo and Valeri Afanas'ev and Michel Houssa and Jean-Pierre Locquet},
journal= {arXiv preprint arXiv:2201.07569},
year = {2022}
}