Insights into structural stability and thermal energy conversion into electrical properties of Mg₃X₂ (X = P, As, and Sb) compounds: A first-principles study

Thermoelectric (TE) materials that convert heat directly into electricity are crucial for waste heat recovery and renewable energy applications. This study focuses on Mg 3 X 2 ([Formula: see text], As, and Sb) compounds, which have emerged as promising candidates for TE applications due to their abundance, non-toxicity, and potential for high efficiency across a broad temperature range. We employed density functional theory and the VASP simulation code to compute the structural, electronic, and TE properties of Mg 3 X 2 compounds. Structural analysis indicates that Mg 3 P 2 and Mg 3 As 2 crystalize in cubic form and Mg 3 Sb 2 acquire a trigonal structure. Mg 3 P 2 and Mg 3 As 2 have direct bandgaps of 1.60 and 1.42[Formula: see text]eV, while Mg 3 Sb 2 has an indirect bandgap of 0.24[Formula: see text]eV. Mg 3 P 2 and Mg 3 As 2 , with their lower thermal conductivities, show high figures of merit (ZT), particularly at low temperatures. Mg 3 Sb 2 , though exhibiting a higher thermal conductivity, demonstrates superior power factors at elevated temperatures. The mechanical stability and phonon dispersion curves analysis confirms that all compounds meet the criteria for structural stability, suggesting their suitability for practical applications. This work highlights the potential of Mg 3 X 2 compounds as viable TE materials and provides insights for future experimental and theoretical studies aimed at improving their performance.