First‐Principles Study of Structural, Electronic, Optical, and Thermoelectric Properties of Alkali‐Metal Bismuthides <scp>XZ</scp> ₂ Bi ₂ (X = K, Rb, Cs; Z = Zn, Cd)

ABSTRACT In this study, a comprehensive investigation of the alkali‐metal bismuthide compounds XZ 2 Bi 2 (X = K, Rb, Cs; Z = Zn, Cd) using full potential augmented plane wave approach performed. The structural properties confirm a tetragonal ThCr 2 Si 2 ‐type crystal symmetry, with systematic variations in crystal lattice parameters influenced by the choice of cation metals. Compounds reveal ductile nature and mechanically stable. Electronic structure analysis reveals metallic behavior, with prominent Bi‐ p states near the Fermi level. Optical studies indicate high reflectivity and dielectric constants in the visible and UV ranges, making these compounds suitable for photonic applications. Thermodynamic properties such as sound velocity, Debye temperature, and heat capacity were computed, showing moderate values consistent with good thermal stability. Moreover, thermoelectric performance evaluated via the Seebeck coefficient, thermal and electrical conductivities, and figure of merit (ZT) reveals basic characteristics of metallic materials with high conductivity and low ZT.