Quasi-two-dimensional features in the phonon spectrum of graphite

The phonon spectrum of graphite is analyzed in detail at the microscopic level and the partial contributions from the displacement of atoms in and perpendicular to the plane of the layers to the phonon density of states are calculated. The main distinctive features of the phonon spectrum of graphite are determined; they are due to the quasi-two-dimensional character of phonon propagation as is characteristic for graphite, specifically, the feature arising in the spectral density as a result of the displacement of atoms along the c axis, analogous to the Dirac singularity in the electron spectrum of graphene. This makes it possible to predict the general changes occurring in the phonon and electron spectra as a result of the intercalation of different metals in graphite as well as to explain the change of the superconducting transition temperature in intercalated graphite. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3170936]