Computational Study of the Electronic, Optical, and Mechanical Properties of InCuX ₂ (X = S, Se, Te) via Ab Initio Methods

First‐principles density functional theory (DFT) calculations were performed to examine the structural, electronic, optical, and mechanical properties of tetragonal InCuX 2 compounds (X = S, Se, Te). The results of the band structure and density of states (DOS) calculations confirm metallic behavior for InCuS 2 , InCuSe 2 , and InCuTe 2 , characterized by a zero band gap, indicating their potential for high conductivity applications. Mulliken population and Hirshfeld charge analyses reveal significant Cu–X covalency and charge delocalization, supporting the metallic nature of these compounds. Bond population analysis further shows that shorter Cu–S bonds (2.33 Å) enhance the structural stability and stiffness of InCuS 2 , while larger chalcogen atomic radii in InCuSe 2 and InCuTe 2 weaken In–X interactions, improving flexibility. The optical analysis highlights high dielectric constants (ε′ ≈ 30 for InCuSe 2 ) and substantial optical absorption (α ≈ 2.5 × 10 5 cm −1 for InCuS 2 ), suggesting their suitability for optoelectronic and photonic applications. Elastic property evaluations show that InCuS 2 possesses the highest stiffness ( C 11 = 235.3 GPa, E = 80.3 GPa), whereas InCuTe 2 exhibits increased ductility ( E = 11.8 GPa). These results demonstrate the tunable metallicity, electrical conductivity, optical response, and mechanical resilience of InCuX 2 materials, positioning them as promising candidates for next‐generation electronic, thermoelectric, and optoelectronic devices.