Band structure induced changes of the dielectric response upon potassium intercalation in graphite studied by inelastic X-ray scattering

The dielectric function ϵ(q,ω) of potassium intercalated graphite (KC8) with q| c-axis was deduced from inelastic X-ray scattering data and compared with ϵ(q,ω) of pristine graphite. A considerable weakening of the first peak of Imϵ(q,ω) upon intercalation was found, which we attribute both to a decreasing overlap of the occupied π-derived states with the empty interlayer states and to an appreciable change of symmetry of the occupied σ-derived states as well as of the empty π-derived states