Quantum chemical studies on Cs3C60 and Cs6C60

The three-dimensional EHMO crystal orbital calculations for crystalline C-6 0, CS3C60 and Cs6C60 are reported. The ground states of both undoped solid C-60 and fully doped Cs6C60 are found to be insulating with an indirect ene rgy gap of 1.2-1.7 and 0.9 eV, respectively. In contrast, CS3C60 forms a me tallic-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 bot h Cs3C60 and Cs6C60 is completely carbonlike. In both cases, the Cs atoms a re almost fully ionized and C-60 molecules form a stable negative charge st ate with three to six additional electrons. Ail the results obtained by us are in excellent agreement with experimental results. (C) 2001 Elsevier Sci ence B.V. All rights reserved.