Thermal Properties of 2D Dirac Materials MN(4) (M = Be and Mg): A First-Principles Study

[Image: see text] Recently, a novel two-dimensional (2D) Dirac material BeN(4) monolayer 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 MN(4) (M = Be and Mg) using first-principles calculations. First, the cohesive energy and phonon dispersion curve confirm the dynamical stability of BeN(4) and MgN(4) monolayers. Besides, BeN(4) and MgN(4) monolayers have the anisotropic lattice thermal conductivities of 842.75 (615.97) W m(–1) K(–1) and 52.66 (21.76) W m(–1) K(–1) along the armchair (zigzag) direction, respectively. The main contribution of the lattice thermal conductivities of BeN(4) and MgN(4) monolayers are from the low frequency phonon branches. Moreover, the average phonon heat capacity, phonon group velocity, and phonon lifetime of BeN(4) monolayer are 3.54 × 10(5) J K(–1) m(–3), 3.61 km s(–1), and 13.64 ps, which are larger than those of MgN(4) monolayer (3.42 × 10(5) J K(–1) m(–3), 3.27 km s(–1), and 1.70 ps), indicating the larger lattice thermal conductivities of BeN(4) monolayer. Furthermore, the mode weighted accumulative Grüneisen parameters (MWGPs) of BeN(4) and MgN(4) monolayers are 2.84 and 5.62, which proves that MgN(4) monolayer has stronger phonon scattering. This investigation will enhance an understanding of thermal properties of MN(4) monolayers and drive the applications of MN(4) monolayers in nanoelectronic devices.