Biphenylene monolayer as a two-dimensional nonbenzenoid carbon allotrope: A first-principles study

TL;DR

This study uses first-principles calculations to explore the structural, electronic, and optical properties of the recently fabricated biphenylene monolayer, revealing its stability, mechanical behavior, and anisotropic electronic characteristics.

Contribution

First detailed theoretical analysis of biphenylene monolayer's properties, providing insights into its stability, mechanical strength, and electronic behavior based on recent experimental synthesis.

Findings

Biphenylene monolayer is structurally stable and dynamically verified.

It exhibits brittle mechanical behavior with a Young's modulus of 0.1 TPa.

The material is metallic with direction-dependent optical properties.

Abstract

In a very recent accomplishment, the two-dimensional form of Biphenylene network (BPN) has been successfully fabricated [Fan et al., Science, 372, 852-856 (2021)]. Motivated by this exciting experimental result on 2D layered BPN structure, herein we perform detailed density functional theory-based first-principles calculations, for the first time, in order to gain insight into the structural, electronic and optical properties of this promising nanomaterial. Our theoretica results reveal the BPN structure is constructed from three rings of tetragon, hexagon and octagon, meanwhile the electron localization function shows very strong bonds between the C atoms in the structure. The dynamical stability of BPN is verified via the phonon band dispersion calculations. The mechanical properties reveal the brittle behavior of BPN monolayer. The Youngs modulus has been computed as 0.1 TPa, which is smaller than the corresponding value of graphene, while the Poissons ratio determined to be 0.26 is larger than that of graphene. The band structure is evaluated to show the electronic features of the material; determining the BPN monolayer as metallic with a band gap of zero. The optical properties (real and imaginary parts of the dielectric function, and the absorption spectrum) uncover BPN as an insulator along the zz direction, while owning metallic properties in xx and yy directions. We anticipate that our discoveries will pave the way to the successful implementation of this new 2D allotrope of carbon in advanced nanoelectronics.