Exploring the Role of Four-Phonon Scattering in the Lattice Thermal Transport of LaMoN 3

In this work, we systematically investigate the lattice thermal conductivity (κ L ) of LaMoN 3 in the C 2/ c and R 3 c phases using first-principles calculations combined with the Boltzmann transport equation. In the C 2/ c phase, κ L exhibits strong anisotropy, with values of 0.75 W/mK, 1.89 W/mK, and 0.82 W/mK along the a, b, and c axes, respectively, at 300 K. In contrast, the R 3 c phase shows nearly isotropic thermal conductivity, with values of 6.28 W/mK, 7.05 W/mK, and 7.31 W/mK along the a, b, and c directions. In both phases, acoustic and low-frequency optical phonons dominate the thermal transport. However, the C 2/ c phase exhibits increased three-phonon scattering leading to smaller values of κ L . Additionally, four-phonon scattering plays a dominant role in the C 2/ c phase, reducing κ L by approximately 96%, whereas in the R 3 c phase, it leads to a smaller but still significant reduction of ∼50%. These results highlight the critical role of four-phonon interactions in determining the thermal transport properties of LaMoN 3 and reveal the stark contrast in thermal conductivity between its two structural phases.