Ultrahigh stiffness and anisotropic Dirac cones in BeN4 and MgN4 monolayers: A first-principles study

TL;DR

This study uses first-principles calculations to reveal that BeN4 and MgN4 monolayers are stable 2D materials with unique electronic properties, ultrahigh stiffness, and potential for energy storage applications.

Contribution

It is the first to demonstrate the stability, electronic structure, and mechanical properties of BeN4 and MgN4 monolayers, highlighting their anisotropic Dirac cones and exceptional mechanical strength.

Findings

BeN4 and MgN4 are dynamically and thermally stable monolayers.

BeN4 exhibits ultrahigh elastic modulus and mechanical strength.

RhN4 nanosheet shows high capacities for Li, Na, and Ca ion storage.

Abstract

Beryllium polynitrides, BeN4 is a novel layered material, which has been most recently fabricated under high pressure (Phys. Rev. Lett. 126(2021), 175501). As a new class of 2D materials, in this work we conduct first-principles calculations to examine the stability and explore the electronic nature of MN4 (M= Be, Mg, Ir, Rh, Ni, Cu, Au, Pd, Pt) monolayers. Acquired results confirm the dynamical and thermal stability of BeN4, MgN4, IrN4, PtN4 and RhN4 monolayers. Interestingly, BeN4 and MgN4 monolayers are found to show anisotropic Dirac cones in their electronic structure. While PtN4 monolayer is predicted to be a narrow band-gap semiconductor, IrN4 and RhN4 monolayers are found to be metallic systems. We also elaborately explore the effects of number of atomic layers on the electronic features of BeN4 nanosheets, which reveal highly appealing physics. Our results highlight that BeN4 nanosheet yield ultrahigh elastic modulus and mechanical strength, outperforming all other carbon-free 2D materials. Notably, RhN4 nanosheet is predicted to yield high capacities of 562, 450 and 900 mAh/g, for Li, Na and Ca ions storages, respectively. This study provides a comprehensive understanding on the intrinsic properties of MN4 nanosheets and highlight their outstanding physics.