Revisiting thermal transport in ThO2 using higher-order thermal transport physics

Abstract

The effect of inclusion of higher-order thermal transport physics (viz. temperature-dependent interatomic force constants, phonon renormalization, and four-phonon scattering) on the computation of phonon frequencies and lattice thermal conductivity of ThO${}_2$ is explored, employing LDA, PBE, and PBEsol exchange–correlational functionals. Upon renormalization, the frequencies are stiffened for the optical phonon modes, whereas the acoustic modes remain unchanged. Thermal conductivity computed using LDA and PBEsol functionals are within 5% of the experimentally measured values at 300 K, whereas that obtained using PBE functional results in an undeprediction of 25%. The temperature-dependent force constants and renormalized phonon frequencies significantly affect the computed lattice thermal conductivity at higher temperatures (40% difference at 1000 K), whereas four-phonon processes have minimal effects (only 10% at 1000 K).