Thermal Properties of 2D Dirac Materials MN4(M = Be and Mg): A First-Principles Study

Abstract

Recently, a novel two-dimensional (2D) Dirac material BeN4monolayer has been fabricated experimentally through high-pressure synthesis. In this work, we investigate the thermal properties of a new class of 2D materials with a chemical formula of MN4(M = Be and Mg) using first-principles calculations. First, the cohesive energy and phonon dispersion curve confirm the dynamical stability of BeN4and MgN4monolayers. Besides, BeN4and MgN4monolayers have the anisotropic lattice thermal conductivities of 842.75 (615.97) W m-1K-1and 52.66 (21.76) W m-1K-1along the armchair (zigzag) direction, respectively. The main contribution of the lattice thermal conductivities of BeN4and MgN4monolayers are from the low frequency phonon branches. Moreover, the average phonon heat capacity, phonon group velocity, and phonon lifetime of BeN4monolayer are 3.54 × 105J K-1m-3, 3.61 km s-1, and 13.64 ps, which are larger than those of MgN4monolayer (3.42 × 105J K-1m-3, 3.27 km s-1, and 1.70 ps), indicating the larger lattice thermal conductivities of BeN4monolayer. Furthermore, the mode weighted accumulative Grüneisen parameters (MWGPs) of BeN4and MgN4monolayers are 2.84 and 5.62, which proves that MgN4monolayer has stronger phonon scattering. This investigation will enhance an understanding of thermal properties of MN4monolayers and drive the applications of MN4monolayers in nanoelectronic devices.