Nonperturbative phonon scatterings and the two-channel thermal transport in Tl3VSe4

Abstract

We study the role of nonperturbative phonon scattering in strongly anharmonic materials having ultralow lattice thermal conductivity with unusual temperature dependence. We take Tl 3 VSe 4 as an example and investigate its lattice dynamics using perturbation theory (PT) up to the fourth order and molecular dynamics (MD) with a machine-learning potential. We find distinct differences of phonon linewidth between PT and MD in the whole Brillouin zone. The comparison between the theoretical phonon linewidths and experiments suggests that PT severely underestimates the phonon scatterings, even when the fourth-order anharmonicity is included. Moreover, we extend our calculations to higher temperatures and evaluate the two-channel thermal conductivity based on the unified theory developed by Simoncelli et al. [Nat. Phys. 15, 809 (2019)]. We find a crucial coherence contribution to the total thermal conductivity at high temperatures. Our results pave the path for future studies of phonon properties and lattice thermal conductivities of strongly anharmonic crystals beyond the conventional PT realm.

Neuroevolution machine learning potentials: Combining high accuracy and low cost in atomistic simulations and application to heat transport

“…The predictions by NEP agree well with the experimental data [91,92]. BTE calculations with force constants from DFT [90] or the GAP-SOAP potential [59] considering both three-phonon and four-phonon scatterings also produce comparable results. However, if only three-phonon scattering is considered in the BTE calculations [90], the obtained lattice thermal conductivity values are about two times as large.…”

“…This indicates the importance of four-phonon scattering in PbTe. In some other materials such as Tl 3 VSe 4 , it has been suggested that the perturbation theory as adopted in the BTE approach can severely underestimate the phonon scatterings even when four-phonon scattering is included [59]. Because phonon anharmonicity is fully taken into account in MD simulations, we expect that our efficient NEP potential will serve as a promising tool for investigating heat transport properties in materials with strong phonon anharmonicity.…”

“…Virial data were not used for PbTe. This training set has been used to train a GAP-SOAP potential for PbTe [59].…”

“…MD simulations with ML potentials have been applied to study heat transport properties of a number of materials, including, e.g., GeTe and MnGe compounds [61][62][63][64], diamond and amorphous silicon [65][66][67], multilayer graphene [68], monolayer silicene [69], CoSb 3 [70], monolayer MoS 2 and MoSe 2 and their alloys [71], C 3 N [72], α-Ag 2 Se [73,74], β-Ga 2 O 3 [75], Tl 3 VSe 4 [59], PbTe [59], and SnSe [76]. There are also works that exclusively used the Boaltzmann transport equation (BTE) approach to calculate thermal conductivity based on force constants determined from ML potentials [77][78][79][80][81][82].…”

“…The area between the two horizontal lines represents the range of values predicted by BTE-DFT calculations. Lattice thermal conductivity of bulk PbTe as a function of temperature, from HNEMD simulations with the NEP potential, from BTE calculations with the GAP-SOAP potential considering both three-phonon and four-phonon scatterings [59], from BTE-DFT calculations considering three-phonon scattering only or both three-phonon and four-phonon scatterings [90] and from experiments [91,92].…”