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 (κ_l) 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 κ_l 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 κ_l 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.