The phonon dispersion of graphite by inelastic x-ray scattering

TL;DR

This study provides comprehensive in-plane phonon dispersion data for graphite using inelastic x-ray scattering, revealing a Kohn anomaly and improving force-constants models for graphite and carbon nanotubes.

Contribution

It presents the first detailed phonon dispersion including the mid-frequency range between K and M points, and supports the existence of a Kohn anomaly at K.

Findings

Full phonon dispersion data for graphite obtained

Evidence supporting a Kohn anomaly at the K point

Enhanced force-constants model for graphite and nanotubes

Abstract

We present the full in-plane phonon dispersion of graphite obtained from inelastic x-ray scattering, including the optical and acoustic branches, as well as the mid-frequency range between the $K$ and $M$ points in the Brillouin zone, where experimental data have been unavailable so far. The existence of a Kohn anomaly at the $K$ point is further supported. We fit a fifth-nearest neighbour force-constants model to the experimental data, making improved force-constants calculations of the phonon dispersion in both graphite and carbon nanotubes available.