Unveiling the thermoelectric potential of Ag3AuSeS: A first-principles approach toward efficient energy conversion

Abstract

The structural, mechanical, electronic, optical, and thermoelectric properties of the quaternary chalcogenide Ag₃AuSeS were systematically investigated using density functional theory combined with Boltzmann transport calculations. The negative formation and cohesive energies, together with the elastic constants and phonon spectra, confirm the thermodynamic, mechanical, and dynamical stability of the compound. The material is ductile in nature and exhibits a low Debye temperature (184 K), indicating favorable phonon scattering. Electronic structure analysis shows that Ag₃AuSeS is a direct band gap semiconductor (1.22 eV) with light electron and moderate hole effective masses, suggesting efficient charge transport. The optical response displays a sharp absorption edge near 1.20 eV and strong absorption in the ultraviolet region, supporting its suitability for optoelectronic applications. Importantly, the compound demonstrates an ultralow lattice thermal conductivity of 0.17 Wm⁻¹K⁻¹at 900 K, combined with a large Seebeck coefficient (∼1550 μVK⁻¹ at 300 K), resulting in a figure of merit that rises from 0.37 at 300 K to 0.85 at 900 K. These results establish Ag₃AuSeS as a promising, lead-free candidate for next-generation thermoelectric and optoelectronic devices.