Phonons in the Graphite-Potassium Intercalation CompoundC36K

An inelastic-neutron-scattering study of the [001] L phonons in ${\mathrm{C}}_{36}$K shows, for the first time, zone-folding effects along with frequency gaps between acoustic and optic modes. Phonon dispersion and structure factors can be modeled by a linear chain with two different masses and two force constants: ${\varphi }_1=3450\mathrm{}$ dyn/cm for the coupling of graphite and potassium planes, and ${\varphi }_2=2850\mathrm{}$ dyn/cm for the coupling between two adjacent graphite planes.