Anomalous phonon thermal transport in boron chalcogenides: Role of four-phonon scattering

Abstract

We report the phonon thermal transport properties of two-dimensional (2D) and bulk boron chalcogenides using the density functional theory-driven Boltzmann transport equation approach by considering three- and four-phonon scatterings. The calculated thermal conductivities for 2D boron sulphide (BS), boron selenide (BSe), and boron telluride (BTe) at 300 K are 210, 57, and 125 W/m K and vary non-monotonically with the chalcogen mass. The effect of four-phonon scattering is significant in all materials and the obtained thermal conductivities are overpredicted by as much as 83% when only three-phonon scattering is included. For bulk BS, the four-phonon scattering is significant for the cross-plane direction (64% reduction in thermal conductivity with four-phonon scattering) while the basal-plane transport stays unaffected (∼10% change). The phonons contributing to the cross-plane thermal transport in bulk BS has similar mean free paths as those for basal-plane transport, despite the two orders of magnitude lower thermal conductivity in the cross-plane direction.