Phonon Spectrum of Second Stage Graphite-Bromine Intercalation Compounds

Coherent inelastic neutron scattering results on the second-stage graphite intercalation compound C8Br are presented. Phonons polarized along the c-axis and in the basal plane were observed. A phenomenological Born-von Karman force constant model with non-axial symmetry is used with parameters adjusted in agreement with the results. Several specific points of the phonon spectrum which are outside of the limits of the model are discussed.