Theoretical Exploration of Stable Semiconducting Ag₂GeXF₆ (X = Sn, Si) Fluorinated Double Perovskites Using Density Functional Theory

In this work, the structural, electronic, and stability characteristics of the semiconducting double perovskite compounds Ag₂GeXF₆ (X = Sn, Si) have been systematically investigated using Density Functional Theory (DFT). The optimized structural parameters confirm that both compounds are crystallographically and thermodynamically stable, making them promising candidates for electronic and optoelectronic applications. The electronic band structure and density of states analyses reveal semiconducting behavior with band gaps of 0.575 eV for Ag₂GeSnF₆ and 0.972 eV for Ag₂GeSiF₆, respectively. These band gaps fall within an ideal range for potential applications in infrared and visible light optoelectronics, suggesting tunable electronic properties through chemical substitution at the X-site. The relatively smaller band gap of Ag₂GeSnF₆ indicates a stronger covalent interaction and enhanced carrier mobility, whereas Ag₂GeSiF₆ exhibits a wider band gap suitable for energy conversion and photonic devices. The stability and favorable electronic features highlight these Ag₂GeXF₆ compounds as robust and versatile semiconducting materials, contributing valuable insight toward the design of next-generation functional materials based on fluorinated double perovskite frameworks.