A theoretical study of the orientational in-plane ordering in stage-2 graphite intercalation compounds is developed with particular emphasis on the role of phonons. Phonon dispersion curves are calculated within a simple phenomenological model. The rotation angle of intercalant layers relative to the graphite layers in the reciprocal-lattice space is shown to be determined predominantly by the transverse-acoustic mode. The rotation angles calculated for CsC24, RbC24, and KC24 are in fairly good agreement with experiments. The rotation angle depends also on the lattice constants of the host and guest layers. Our calculations have been carried out assuming a homogeneous triangular lattice structure for the intercalant layer. Comment is, therefore, made on the possibility of having a domain structure in which locally registered domains are bounded by discommensurations.
ASJC Scopus subject areas
- Condensed Matter Physics