DFT pressured BaTiO3 calculation using WC and HSE functionals and ONCV pseudopotentials

Abstract

Theoretical BaTiO3 (BTO) single crystal with tetragonal phase was studied as a function of tensile and compressive pressure using Wu-Cohen (WC) and Heyd–Scuseria–Ernzerhof (HSE) exchange-correlational functional and the optimized norm-conserving Vanderbilt (ONCV) pseudopotentials. The results show different physical property anomalies associated with possible phase transitions. The lattice parameters evidence an anomaly at −7 GPa corresponding to the known super-tetragonality transition reported by Tinte et al. and Kvasov et al. [21]. The tetragonality coefficient indicates an apparent cubic phase at P= +2.17 GPa, however, the different Ti-O bond lengths and the phonons associated with the optical modes in the Brillouin zone center suggest that symmetric order of cubic phase is not reached in this pressure. While an additional anomaly at +7 GPa seems to be related to a well-ordered cubic structure. Furthermore, Löwdin atomic population analysis with variation in hydrostatic pressure provided information on the behavior of chemical bonds in BTO. Finally, the theoretical results are compared with those experimentally reported in the literature.