Structural phase transitions and dielectric properties of BaTiO3 from a second-principles method

Barium titanate ($\mathrm{BaTi}{\mathrm{O}}_{3}$, BTO) is a typical ferroelectric material with a series of complex phase transitions. Understanding its phase transitions and related properties from an atomic perspective is of scientific significance and practical importance. In this paper, based on first-principles calculation, a second-principles model is constructed to investigate the phase transition and related properties of BTO at the atomic level. By using the constructed second-principles model, the full phase-transition sequence from high-temperature paraelectric cubic phase to the low-temperature rhombohedral phase through tetragonal and orthorhombic intermediate phases have been successfully predicted at the atomic level. To reveal the underlying mechanism of phase transition, the influences of different anharmonic terms on phase transition are investigated in detail. We found that the interaction between strain and Ti-O bond plays an essential role in phase transition. Furthermore, dielectric properties and the $P\text{\ensuremath{-}}E$ loop of BTO are successfully obtained with the model. In this paper, we not only provide a model to predict the phase transitions and related properties of BTO from the atomic level but also extend the application of the second-principles method.