First-principles study of stability and electronic properties of single-element 2D materials

D C Hvazdouski

doi:10.35596/1729-7648-2021-19-8-92-98

Abstract

We have estimated stability of single-element 2D materials (C2, N2, Si2, P2, Ge2, As2, Sn2, Sb2, Pb2, and Bi2) by ab initio calculations. The calculations of structural and mechanical properties of 2D materials were performed using the VASP software package. The results of calculations of stiffness tensors, Young's modulus, and Poisson's ratios show that all studied single-element 2D materials are mechanically stable. Dynamic stability was investigated by calculating the phonon dispersion of the materials using the finite displacement method. Only Pb2 has imaginary modes in the phonon dispersion curves and therefore it has dynamic unstable structure at low temperatures. The analysis of the band structures indicates the presence of insulators (N2), semiconductors (P2, As2, Bi2, Sb2), semimetals, and metals among the studied group of single-element 2D materials.

Highlights

Thin two-dimensional (2D) materials have made their way to the forefront of several research areas including batteries, electrocatalysis, electronics, and photonics [1]
Almost all single-element 2D materials do not have imaginary frequencies in the phonon dispersion curves and they can be viewed as dynamically stable structures
Pb2 has imaginary frequencies in the vicinity of the Γ, M, and K points indicating instability against phonon excitation. This indicates that Pb2 is unstable at low temperatures

Summary

Introduction

Thin two-dimensional (2D) materials have made their way to the forefront of several research areas including batteries, electrocatalysis, electronics, and photonics [1]. This development has been prompted by tunable properties of atomically thin crystals. More than fifty compounds have been synthesized or exfoliated as single layers These include the well-known single-elemental crystals and their ligand functionalized derivatives, transition metal dichalcogenides, transition metal carbides and -nitrides, group III–V semiconductors and insulators, transition metal halides, post-transition metal chalcogenides, and organic-inorganic hybrid perovskites. In this work we performed a series of ab initio calculations to investigate the stability and electronic properties of single-elemental 2D materials previously unknown and potentially synthesizable monolayers

Methods of calculation

N2 Si2 P2 Ge2 As2 Sn2 Sb2 Pb2 Bi2

Conclusion