DFT analysis of Ba2XTaO6 (X = Sm, Er) perovskites: Stability & functional properties

Abstract

In this article, the structural, phonon, electronic, optical, magnetic, elastic and thermal properties of the double perovskites Ba₂XTaO₆ (X = Sm or Er) are studied using density functional theory (DFT) within the WIEN2k. According to the structural data, both compounds crystallize in a stable cubic phase with optimized lattice parameters of 8.70 Å for Ba₂SmTaO₆ and 8.49 Å for Ba₂ErTaO₆ in the ferromagnetic (FM) state. Phonon dispersion calculations confirm that both compounds are dynamically stable and can therefore be experimentally synthesized. Band-structure calculations reveal that, Ba₂SmTaO₆ has a wide-bandgap semiconductor having bandgap values of 2.8 eV (PBE), 3.6 eV (PBE + mBJ), and 2.87 eV (PBE + U), while Ba₂ErTaO₆ behaves as an insulator. Optical properties reveal a great index of refraction and profound absorption in the ultraviolet region, indicating their usefulness in optoelectronic applications. Magnetic studies yield total magnetic moments of 5.00 μB for Ba₂SmTaO₆ and 3.00 μB for Ba₂ErTaO₆, deriving primarily from the rare-earth ions. The assessment of the elastic property confirms their mechanical stability, with bulk moduli of 117 GPa for Ba₂SmTaO₆ and 145 GPa for Ba₂ErTaO₆, reinforcing their structural strength. This study lends credence to prospecting possibilities of these materials in application to optoelectronics, spintronics, and high-temperature environments.