Lenosky's energy and the phonon dispersion of graphene

TL;DR

This paper evaluates Lenosky's energy model for graphene's phonon spectrum, highlighting its strengths in flexural modes and identifying the need for an additional term to accurately reproduce the full phonon dispersion.

Contribution

It provides a detailed comparison of Lenosky's model with experimental data and other models, revealing its limitations and suggesting improvements.

Findings

Accurately describes flexural phonon modes in graphene.

Requires an extra energy term for full phonon dispersion accuracy.

Shows better performance than previous models in certain aspects.

Abstract

We calculate the phonon spectrum for a graphene sheet resulting from the model proposed by T. Lenosky et al. (Nature 355, 333 (1992)) for the free energy of the lattice. This model takes into account not only the usual bond bending and stretching terms, but captures the possible misalignment of the pz orbitals. We compare our results with previous models used in the literature and with available experimental data. We show that while this model provides an excellent description of the flexural modes in graphene, an extra term in the energy is needed for it to be able to reproduce the full phonon dispersion correctly beyond the Gamma point.