Quantum chemical studies on Cs 3C 60 and Cs 6C 60

Abstract

The three-dimensional EHMO crystal orbital calculations for crystalline C 60, Cs 3C 60 and Cs 6C 60 are reported. The ground states of both undoped solid C 60 and fully doped Cs 6C 60 are found to be insulating with an indirect energy gap of 1.2–1.7 and 0.9 eV, respectively. In contrast, Cs 3C 60 forms a metallic-conducting phase with a set of three half-filled bands crossing the Fermi level, which is found to be located close to a peak of the density of state (DOS). The character of crystal orbital near the Fermi level for both Cs 3C 60 and Cs 6C 60 is completely carbonlike. In both cases, the Cs atoms are almost fully ionized and C 60 molecules form a stable negative charge state with three to six additional electrons. All the results obtained by us are in excellent agreement with experimental results.