Structural, electronic, optical, and mechanical properties of potassium-based fluoro-perovskites (X Be, Zn, Sr): A first-principles study

Using first-principles calculations, we investigated the structural, electrical, optical, and mechanical properties of the potassium-based fluoro-perovskite KX . Our results revealed that exhibits a direct bandgap with a value of 5.49 eV. In contrast, and display indirect bandgap, with values of 7.95 eV and 3.54 eV, respectively. Through density of states analysis, we identified that these materials’ valence band maxima (VBMs) are primarily derived from the p orbitals of fluorine. Due to fluorine's high electronegativity, its p orbitals are at very low energy levels, resulting in low VBMs corresponding to substantial bandgaps. Optical assessments reveal high optical conductivity in KXF₃, suggesting its applicability in optoelectronic devices, while analyses of reflectivity and refractive index highlight their potential utility in optical coatings and UV protection. Mechanical evaluations confirm the stability and ductility of the compounds, with demonstrating superior machinability and exhibiting notable anisotropic properties.