Theoretical investigation of the electronic properties of potassium graphite

Abstract

We present the results of a band-structure calculation for the first-stage graphite-intercalation compound of potassium, K${\mathrm{C}}_8$. A modified Korringa-Kohn-Rostoker formalism which was applied successfully to Li${\mathrm{C}}_6$ has been used. To good approximation, the K${\mathrm{C}}_8$ bands are given by those of two-dimensional graphite folded into the smaller Brillouin zone of K${\mathrm{C}}_8$, with $\frac{1}{8}$ 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 $E_F$. 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 K${\mathrm{C}}_8$ 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 K${\mathrm{C}}_8$.