Layer breathing and shear modes in multilayer graphene: A DFT-vdW study

TL;DR

This study uses advanced density-functional theory with van der Waals functionals to accurately analyze the vibrational and structural properties of multilayer graphene, focusing on layer breathing and shear modes.

Contribution

It identifies the most effective vdW functional for predicting vibrational properties and demonstrates its predictive power for interlayer modes in multilayer graphene.

Findings

vdW-DF1-optB88 performs best among tested functionals

Calculated interlayer vibrational frequencies match experimental data

Functional accurately predicts unmeasured layer-breathing and shear modes

Abstract

In this work, we study structural and vibrational properties of multilayer graphene using density-functional theory (DFT) with van der Waals (vdW) functionals. Initially, we analyze how different vdW functionals compare by evaluating the lattice parameters, elastic constants and vibrational frequencies of low energy optical modes of graphite. Our results indicate that the vdW-DF1-optB88 functional has the best overall performance on the description of vibrational properties. Next, we use this functional to study the influence of the vdW interactions on the structural and vibrational properties of multilayer graphene. Specifically, we evaluate binding energies, interlayer distances and phonon frequencies of layer breathing and shear modes. We observe excellent agreement between our calculated results and available experimental data, which suggests that this functional has truly predictive power for layer-breathing and shear frequencies that have not been measured yet. This indicates that careful selected vdW functionals can describe interlayer bonding in graphene-related systems with good accuracy.