Effect of four-phonon scattering on thermal transport of <i>γ</i>-graphyne revealed by atomic cluster expansion

In this work, we systematically explore the effect of four-phonon (4ph) scattering on the lattice thermal conductivity (κl) of γ-graphyne based on the atomic cluster expansion potential for carbon (C-ACE) combined with a phonon Boltzmann transport equation. The reliability of C-ACE in assessing the thermal transport properties of γ-graphyne is confirmed through comparing the results of phonon dispersion relation and κ3ph (only considering 3ph scattering) derived from C-ACE and density functional theory calculations. Regular residual analysis indicates that there might exist a strong 4ph interaction in γ-graphyne, and calculations further demonstrate κ3ph+4ph (considering 3ph scattering in an iterative solution and 4ph scattering in relaxation time approximation) is indeed reduced by 69.8% relative to κ3ph. From the analysis of scattering rates in γ-graphyne, one can intuitively observed that the 4ph scattering occupies a highly significant position in total phonon scattering, which greatly suppresses the κl. The strong 4ph scattering in γ-graphyne is primarily due to the reflection symmetry selection rule less restricts 4ph scattering process for an out-of-plane flexural acoustic mode. The findings presented in this work demonstrate the reliability of C-ACE based accelerated calculations on the κl of γ-graphyne, as well as reveal that the strong 4ph scattering in γ-graphyne significantly reduces its κl, which will greatly promote the application of γ-graphyne and graphyne family in the field of thermoelectricity.