First-principles study on the lattice thermal conductivity of layered Dirac semimetal BeN4

Abstract

A novel two-dimensional Dirac semimetal BeN 4 was successfully synthesized in a recent experiment (Bykov et al. Phys. Rev. Lett. 126, 175501 (2021)). Here, we have studied the lattice thermal conductivities of bulk BeN 4 by the first-principles calculations. Due to the anisotropic crystal structure, the lattice thermal conductivities of BeN 4 show large anisotropy and the values at 300 K are 91.5, 42.1, and 5.0 W/m ⋅ K along the armchair, zigzag, and cross-plane directions respectively based on the three-phonon scattering. We also find that four-phonon scattering only reduces the lattice thermal conductivities of BeN 4 by about 9%. Due to the relatively weak Be-N bonds and complex crystal structure, BeN 4 has small phonon group velocities and large phonon anharmonicity, resulting in its much lower lattice thermal conductivity than that of hexagonal boron nitride and graphene. Our work would be helpful for future experimental and theoretical studies on the Dirac semimetal BeN 4 . • The lattice thermal conductivity of Dirac semi-metal BeN 4 was studied by the first-principles calculations. • BeN 4 has large anisotropic thermal conductivity due to its anisotropic crystal structure. • Despite the light elements, BeN 4 has a relatively low lattice thermal conductivity due to its large anharmonicity.