Atomistic simulations of structural and thermodynamic properties of bilayer graphene

TL;DR

This study uses Monte Carlo simulations to analyze the structural and thermodynamic properties of bilayer graphene, revealing temperature-dependent behaviors and differences from single-layer graphene.

Contribution

It provides new insights into the temperature dependence of lattice parameters, bending rigidity, and out-of-plane fluctuations of bilayer graphene using empirical potential simulations.

Findings

Thermal expansion coefficient becomes positive above ~400 K.

Bending rigidity is twice that of single-layer graphene.

Out-of-plane fluctuations transition from correlated to uncorrelated at ~3 nm$^{-1}$ wavevector.

Abstract

We study the structural and thermodynamic properties of bilayer graphene, a prototype two-layer membrane, by means of Monte Carlo simulations based on the empirical bond order potential LCBOPII. We present the temperature dependence of lattice parameter, bending rigidity and high temperature heat capacity as well as the correlation function of out-of-plane atomic displacements. The thermal expansion coefficient changes sign from negative to positive above $\approx 400$ K, which is lower than previously found for single layer graphene and close to the experimental value of bulk graphite. The bending rigidity is twice as large than for single layer graphene, making the out-of-plane fluctuations smaller. The crossover from correlated to uncorrelated out-of-plane fluctuations of the two carbon planes occurs for wavevectors shorter than $\approx 3$ nm$^{-1}$