Effects of high-order anharmonicity on the thermal transport in AgX (X=Cl, Br, I)

Recent studies showed the suppression of third-order anharmonicity can lead to an important role of the four-phonon scattering process on the thermal transport of solids. Herein, we investigate the lattice dynamics and thermal transport in AgX (X=Cl, Br, I) using perturbation theory up to the fourth order and a unified theory of thermal transport including population and coherence contributions. We find that the temperature renormalization of third-order force constants is significant for calculating the lattice thermal conductivities of AgCl and AgBr. Our results also show that the lattice thermal conductivity of AgI is overestimated even including fourth-order anharmonicity. Further simulation based on a force-constant potential suggests an important role of the fifth- and sixth-order phonon scattering processes in the lattice thermal transport of AgI.