ELECTRONIC-STRUCTURE OF CRYSTALLINE K6C60

First-principles electronic-structure calculations for crystalline K6C60 are reported, based on the geometry determined by x-ray-diffraction measurements. The ground state is found to be insulating, with an indirect gap of 0.48 eV. The character of both occupied and unoccupied states near the valence-band maximum is completely carbonlike. The K atoms are almost fully ionized, and the C60 molecule is stabilized in an unusually high charge state with six additional electrons. Implications of the distribution of excess charge on the C60 molecule for orientational ordering are discussed.