Effects of local chemical ordering on the thermal transport in entropy-regulated PbSe-based thermoelectric materials

Configurational entropy manipulation strategy has been proposed for designing high-performance thermoelectric materials. Understanding the phase stability is essential to regulate the thermal conductivity for optimizing the thermoelectric performance. Herein, the lattice thermal conductivity of PbSe is found to decrease from 1.87 to 0.76 Wm−1 K−1 of PbSe0.5Te0.25S0.25, which mainly results from the decreased contribution from the phonon modes in the frequency range of 0.5–2 THz. Moreover, we find local chemical ordering (LCO) in PbSe0.5Te0.25S0.25 by conducting hybrid Monte Carlo and molecular dynamics simulations based on our constructed machine-learning interatomic potential. The local chemical ordering can reduce phonon scattering with frequency in 0–2 THz, thus enhancing thermal conductivity by approximately 14%. This work unfolds the energy favorable structure with LCO in entropy-tailored thermoelectric material, which gives guidance for regulating thermal transport.