Theoretical investigation of the electronic properties of potassium graphite

We present the results of a band-structure calculation for the first-stage graphite-intercalation compound of potassium, KC₈. A modified Korringa-Kohn-Rostoker formalism which was applied successfully to LiC₆ has been used. To good approximation, the KC₈ bands are given by those of two-dimensional graphite folded into the smaller Brillouin zone of KC₈, with 1/8 of an extra electron per C atom. The K $3p$ states lead to a dispersionless set of bands 14 eV below the Fermi level, and the K $4s$ states create an isotropic, parabolic band with a minimum 1.8 eV above EF. Hybridization of K states with the filled C bands is fairly weak but has a noticeable effect on the band dispersion at the Fermi level. From our band calculation we extract the KC₈ density of states, the Fermi surface, de Haas---van Alphen frequencies and masses, and plasma frequencies. We find fairly good agreement with the experimental de Haas---van Alphen frequencies, but our calculated density of states at the Fermi level is smaller than that obtained from low-temperature specific heat. We compare our work with other experimental and theoretical studies of KC₈.