First-principles calculations to investigate Structural, Electronic, optical and mechanical properties of Cu-based fluoroperovskite XCuF₃ (X = K, Ru)

The structural, electronic, and optical properties of cubic fluoro perovskites XCuF₃ (X = K, Rb) are examined using density functional theory as implemented in the CASTEP code. The PBE-GGA exchange–correlation function was employed to investigate the aforementioned properties. The optimization of the crystal structure yielded lattice constants of 4.13 and 4.19 Å for KCuF₃ and RbCuF₃, respectively. The indirect band gap is reported in both materials with a value of 3.42 and 3.64 eV for KCuF₃ and RbCuF₃, respectively. The density of states shows that the valence band is formed by the contributions from p and d-orbitals, whereas the conduction band is formed primarily by contributions from s and p-orbitals. It is observed that RbCuF₃ absorbs the incident photons more abruptly than KCuF₃. The refractive index showed that RbCuF₃ is more transparent than KCuF₃. The reflectivity showed that RbCuF₃ can effectively bounce back the incident radiations. Due to their larger band gaps, both materials can effectively absorb ultraviolet radiation. Moreover, RbCuF₃ may also serve as a coating layer for reflective applications because of its highly reflective surface.