Finite temperature lattice properties of graphene beyond the quasiharmonic approximation

TL;DR

This study uses atomistic Monte Carlo simulations to explore the temperature-dependent lattice and mechanical properties of graphene, revealing non-monotonic behaviors beyond the quasiharmonic approximation.

Contribution

It introduces a method to analyze graphene's properties at finite temperatures beyond traditional approximations, predicting novel non-monotonic behaviors.

Findings

Lattice parameter shows a minimum at ~900 K.

Shear modulus exhibits a maximum at ~900 K.

Poisson ratio remains small (~0.1) across a broad temperature range.

Abstract

The thermal and mechanical stability of graphene is important for many potential applications in nanotechnology. We calculate the temperature dependence of lattice parameter, elastic properties and heat capacity by means of atomistic Monte Carlo simulations that allow to go beyond the quasiharmonic approximation. We predict an unusual, non-monotonic, behavior of the lattice parameter with minimum at temperature about 900 K and of the shear modulus with maximum at the same temperature. The Poisson ratio in graphene is found to be small ~0.1 in a broad temperature interval.