Lattice-dynamical model for alkali-metal—graphite intercalation compounds

The phonon dispersion curves for graphite intercalation compounds (GIC's) are calculated for the case of potassium, rubidium, and cesium intercalates. The model is based on the staging periodicity in these compounds in that it assumes that the symmetry of the graphite crystal is preserved upon intercalation. The effect of intercalation is, therefore, aken into account by a $k_z$-axis zone folding of the graphite dynamical matrix. The resulting phonon dispersion curves yield results in agreement with all the reported data on GIC's, derived from neutron scattering and specific-heat measurements, and first- and second-order Raman scattering experiments.