First principles study of the structural and electronic properties of double perovskite Ba sub(2)YTaO sub(6) in cubic and tetragonal phases

The Ba sub(2)YTaO sub(6) double perovskite presents a transition from cubic (Fm - 3m) to tetragonal structure (14/m) at high temperature. In this work, we present a detailed study of the structural and electronic properties of the double perovskite Ba sub(2)YTaO sub(6) in space group Fm-3m and 14/m. Calculations were made with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient (CCA) and Local Density (LDA) approximations. From the minimization of energy as a function of volume and the fitting of the Murnaghan equation some structural characteristics were determined as, for example, total energy, lattice parameter (a=8.50 A in cubic phase and a=5.985 A and c=8.576 A in tetragonal), bulk modulus (135.6 GPa in cubic phase and 134.1 GPa in tetragonal phase) and its derivative. The study of the electronic characteristics was performed from the analysis of the electronic density of states (DOS). We find a non-metallic behavior for this with a direct band gap of approximately 3.5 eV and we found that the Ba sub(2)YTaO sub(6) (14/m) phase is the most stable one.