Effects of Four-Phonon Scattering and Wave-like Phonon Tunneling Effects on Thermoelectric Properties of Mg2GeSe4 using Machine Learning

TL;DR

This study introduces a machine-learning framework to rapidly predict lattice thermal conductivity, including complex four-phonon and wave-like effects, applied to Mg2GeSe4, revealing insights into its thermoelectric performance and guiding material discovery.

Contribution

We develop a machine-learning interatomic potential that accelerates thermal conductivity predictions, incorporating four-phonon and wave-like effects, enabling efficient thermoelectric material analysis.

Findings

Four-phonon scattering reduces thermal conductivity by over 22% at 300K.

Wave-like phonon contributions increase with temperature.

Mg2GeSe4 achieves a maximum zT of 0.49 at 900K.

Abstract

We present a machine-learning interatomic potential (MLIP) framework, which substantially accelerates the prediction of lattice thermal conductivity for both particle-like and wave-like thermal transport, including three-phonon and four-phonon scattering processes, and achieves speedups of five orders of magnitude compared to the conventional DFT calculations. We illustrate our approach through an in-depth study of Mg2GeSe4 as an exemplar thermoelectric material. Four phonon scattering is found to reduce lattice thermal conductivity by 22.5% at 300K and 26.7% at 900 K. The particle-like contribution to lattice thermal conductivity decreases, while the wave-like component increases with increasing temperature. The maximum figure of merit zT at 900K is found to be 0.49 for the n-type and 0.45 for the p-type Mg2GeSe4, respectively. Our analysis reveals that a substantial contribution to the Seebeck coefficient is driven by multi-band features in the valence band. Our study gives insight into the promising thermoelectric performance of Mg2GeSe4 and provides an efficient and accurate scheme for developing rational materials discovery strategies and practical applications of thermoelectric materials.