DFT-based investigation of SrFAgX (X = S, Se, Te) semiconductors: structural, electronic, elastic, and optical properties for emerging optoelectronic and spintronic applications

This study presents a comprehensive first-principles investigation of SrFAgX (X = S, Se, Te) semiconductors, focusing on the effect of chalcogen substitution on structural, elastic, electronic, and optical behavior. Using DFT-GGA calculations, we uncover systematic structure-property relationships, pressure-induced band gap tuning, and anisotropic compressibility across the series. These findings reveal how electronic and optical features can be tailored for targeted optoelectronic and spintronic applications within the generalized gradient approximation (GGA). The structural parameters, including lattice constants and internal atomic positions, show good agreement with experimental data, confirming the reliability of the computational model. The elastic constants and related mechanical moduli reveal that SrFAgS is the stiffest compound, while SrFAgSe exhibits higher flexibility, indicating tunable mechanical behavior depending on the chalcogen element. Electronic band structure analysis demonstrates that all three compounds have direct band gaps, which decrease systematically from S to Te due to enhanced orbital interactions. The calculated partial and total density of states highlight significant contributions from Ag-d and X-p states near the Fermi level, indicating strong hybridization effects. Optical properties, including dielectric function, absorption coefficient, reflectivity, refractive index, and optical conductivity, reveal systematic trends across the series, showing an enhanced optical response in SrFAgTe. These findings establish a foundation for understanding the chalcogen-dependent behavior of these materials and highlight their potential for optoelectronic, thermoelectric, and spintronic applications.