A multiscale computational approach to the thermoelectric of β-Cu2Se: Combining DFT+U and molecular dynamics

Thermoelectric materials offer a direct pathway for mitigating the global energy crisis by converting waste heat into usable electricity; however, their efficiency must be improved for largescale applications. To this end, we evaluate the high-potential material β-Cu2Se through an integrated multiscale computational approach combining first-principles DFT+U calculations and molecular dynamics (MD) simulations. Our results reveal that β-Cu2Se exhibits semiconducting behavior with a direct band gap of approximately 1.3 eV. The lattice thermal conductivity, κl, calculated via non-equilibrium molecular dynamics, decreases from 0.905 Wm−1 K−1 at 300 K to 0.410 Wm−1 K−1 at 800 K due to the superionic transition and enhanced phonon scattering. Over the temperature range of 300–800 K, the thermoelectric figure of merit, ZT, increases from 0.184 to 0.747, with peak performance at elevated temperatures driven by a high Seebeck coefficient and suppressed thermal conductivity. This study provides the first integrated DFT+U and MD assessment of both electronic and lattice thermal transport in β-Cu2Se, offering a comprehensive evaluation of ZT that bridges the gap between electronic structure calculations and lattice dynamics simulations. Our findings demonstrate that β-Cu2Se possesses favorable thermoelectric performance, making it a strong candidate for mid- to high-temperature energy conversion applications.