Electronic structure, elastic, optical and thermodynamic properties of cubic perovskite NaBaF3 with pressure effects: First-principles calculations

The electronic structure, elastic, optical and thermodynamic properties of cubic perovskite NaBaF3 under high pressure were investigated using the ab initio calculations. The calculated lattice constant (a(0)) and bulk modulus (B-0) at 0 GPa were determined to be 4.278 angstrom and 53.555 GPa, respectively, which are consistent with previous reports. The elastic constants and bulk modulus at high pressure were calculated. According to Pugh's crystal mechanical stability conditions, the phase transition point of NaBaF3 is found to be 68.8 GPa, which has not been reported by any previous paper. The band structure calculations reveal that cubic perovskite NaBaF3 is a direct band-gap material in the pressure range from 0 GPa to 60 GPa. The dielectric function epsilon(omega), absorption coefficient alpha(omega), reflectivity R(omega), transmittance T(omega), absorbance A(omega) and complex refractive index N(omega) at 0 GPa, 20 GPa, 40 GPa and 60 GPa were studied. It is found that the band gap increases with the increasing pressure, and the absorption spectra show blue shift. The Debye temperature at 300 K and the values of the relative volume, heat capacity, bulk modulus, thermal expansion coefficient, heat capacities, and relative Debye temperature with pressures and temperatures effect were investigated. Our results will provide theoretical guidance for the experimental investigations and industrial applications of NaBaF3 in future.