Theoretical Exploration of Si₇X (X = Ge, Sn): Bridging Structural and Energy‐Related Applications

Abstract A comprehensive study is conducted on the structural, mechanical, dynamical, electronic, optical, and thermoelectric properties of Si 7 X (X = Ge and Sn) using first‐principles calculations. Structural analysis confirms the stability of both compounds, while the elastic and mechanical properties reveal their ductile nature. Dynamical stability is verified through phonon dispersion spectra, ensuring the robustness of the predicted phases. Electronic band structure calculations indicate that both Si 7 Ge and Si 7 Sn are semiconductors with direct band gaps of 1.03 and 0.75 eV, respectively. These materials also exhibit excellent optical absorption, with coefficients reaching 10 5 cm −1 , making them ideal for optoelectronic applications. The maximum photoconversion efficiency, determined using the spectroscopic limited maximum efficiency (SLME) method, is calculated to be 30.3% for Si 7 Ge and 23.2% for Si 7 Sn at 300 K. Furthermore, thermoelectric performance is evaluated, with the average figure of merit (ZT) found to be 0.76 for Si 7 Ge and 0.78 for Si 7 Sn, highlighting their potential for renewable energy applications. These results underscore the promise of Si 7 Ge and Si 7 Sn as multifunctional materials for photovoltaic, optoelectronic, and thermoelectric technologies.