First-Principles Investigation of Four-Phonon Scattering Effects on Thermal Transport in Two-Dimensional BeN4

Four-phonon (4 ph) scattering is critically important for describing thermal transport properties in two-dimensional (2D) materials. Incorporating the 4 ph process is crucial for obtaining reliable lattice thermal conductivity (κl) and understanding phonon thermal transport. Among emerging 2D materials, monolayer BeN4 has attracted increasing attention because of its unique structural properties. Here, the influence of 4 ph scattering on the thermal transport behavior of monolayer BeN4 is comprehensively explored through first-principles calculations. The calculated results demonstrate that, after considering the 4 ph scattering, the κl of monolayer BeN4 at 300 K are reduced by 37.7% and 50.6% along the zigzag and armchair directions, respectively. These findings indicate that monolayer BeN4 exhibits anisotropy in thermal transport and that 4 ph scattering has a significant impact on thermal transport. The thermal transport is dominated by acoustic phonon branches. Furthermore, the larger κl at low temperatures originates from longer phonon lifetimes, larger phonon mean free paths, lower phonon scattering rates, and smaller weighted phase space. In addition, the different channels of 4 ph scattering are systematically analyzed, revealing that the redistribution channel provides the dominant contribution to 4 ph scattering. This investigation provides deeper insight into the thermal transport behavior of monolayer BeN4 and facilitates its potential applications in nanoelectronic and thermal management devices.