A New Self-Consistent Band Structure of C8K

The electronic structure of C 8 K is investigated by using the self-consistent numerical-basis-set LCAO method within the local-density-functional formalism. It is found that the graphite π * bands are split in C 8 K and some of them go down below the Fermi energy. As a result there exist three-dimensional Fermi surfaces originating from graphite π * bands in the center of the Brillouin zone. This is due to the charge unbalance between environmentally non-equivalent carbon atoms in a graphite layer, which is produced by the potassium atoms. The new band structure is shown consistent with recent experiments of optical spectra.