The pursuit of environmentally benign and structurally robust alternatives to lead-based perovskites has motivated the investigation of ecofriendly halide double perovskites for next-generation optoelectronic applications. In this work, the structural, mechanical, electronic, and optical properties of the fluoride-based double perovskite Na 2 CuSbF 6 are systematically examined using first-principles density functional theory within the CASTEP framework, employing GGA-PBE, HSE06, and spin-orbit coupling (SOC) approaches. Structural optimization confirms a stable cubic Fm-3m phase with a lattice constant of 8.70 Å. The material satisfies the Born mechanical stability criteria and exhibits ductile behavior with notable elastic anisotropy. Electronic structure analysis reveals an indirect bandgap of 0.471 eV (GGA-PBE), 0.653 eV (HSE06), and 0.323 eV (SOC), indicating suitability for infrared optoelectronic applications. Density of states results show that Cu-3d, Sb-5p, and F-3p orbitals dominate near the Fermi level. Optical properties demonstrate strong absorption, a moderate static dielectric constant (~6.5), low reflectivity (~0.06), and a high refractive index (~2.5), highlighting Na2CuSbF6 as a promising lead-free perovskite for photovoltaic and energy-conversion devices.
Galib et al. (Tue,) studied this question.