Electronic structure of crystallineK6C60

Abstract

First-principles electronic-structure calculations for crystalline ${\mathrm{K}}_6$ ${\mathrm{C}}_{60}$ 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 ${\mathrm{C}}_{60}$ molecule is stabilized in an unusually high charge state with six additional electrons. Implications of the distribution of excess charge on the ${\mathrm{C}}_{60}$ molecule for orientational ordering are discussed.