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

Physica E: Low-dimensional Systems and Nanostructures(2023)

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A novel two-dimensional Dirac semimetal BeN4 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 BeN4 by the first-principles calculations. Due to the anisotropic crystal structure, the lattice thermal conductivities of BeN4 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 BeN4 by about 9%. Due to the relatively weak Be-N bonds and complex crystal structure, BeN4 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 BeN4.
Lattice thermal conductivity,Dirac semimetal,Anharmonicity
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