DIRAC-FOCK-SLATER CALCULATIONS ON THE GEOMETRIC AND ELECTRONIC-STRUCTURE OF NEUTRAL AND MULTIPLY-CHARGED C-60 FULLERENES

Using a self-consistent relativistic molecular Dirac-Fock-Slater metho d we have determined the geometric structures and ionization energies of C-60(X+) (x = 0-7). The lengths of the bonds for the pentagonal edg e (single bonds) and the bonds shared by hexagonal rings (double bonds ) are found to increase as a function of charge state with an expansio n of the cage. The binding energy per atom of C-60(x+) (x = 0-7) shows a quadratic dependence on the charge state of the C-60 cluster and an extrapolation to higher charge states reveals that C-60(x+) Should st ill be bound up to x = 13. Charging of the clusters are analysed using a classical capacitance model and compared with results from other ca lculations. Calculated ionization potentials are found to increase lin early with the charge while the available experimental data with compa ratively big uncertainties indicate a small quadratic dependence.