CHARGE-TRANSFER IN FULLERENE INTERCALATIO N COMPOUNDS

A theoretical study of charge transfer is proposed. We present the res ults of cohesive energy calculations as a function of charge transfer x. The value of x, defined as the electronic fraction transfered from the intercalate to the fullerene, is given by the minimum of the energ y, and corresponds to the most stable structure. The compounds studied are in the form (A(+x))3(C(-x/20))60 or (A(+x))(B(+x))2 (C(-x/20))60, where A and B represent the donor intercalate species (Li, K, Rb, and Cs), and x, the charge transfer. The energy is composed of three cont ributions E(Kinetic), E(Potential) (coulombian + exchange), and E(Made luding). These three contributions are calculated as a function of x. The cohesive energy of fullerene and the energy needed to increase the cubic parameter a are evaluated and compared with the literature's va lues. We also discuss the correlation between charge transfer and supe rconductive temperature T(c), the stability and the maximum value of T (c) for different fullerene donor intercalation compounds.