Electronic structures, geometries, and energetics of highly charged cations of the C60 fullerene

Electronic structure calculations carried out at the HF/6–311G∗ level of theory predict the C602+ and C604+ species to possess D5d and C3 symmetries, respectively. On the other hand, the pentagonally distorted C608+ species undergoes further lowering of symmetry that is readily rationalized by its small HOMO-LUMO gap. Although the C6010+, C6018+, and C6028+ closed-shell icosahedral cages are found stable with respect to a totally symmetrical Coulomb explosion by both ab inito and semiempirical calculations, the MNDO, AM1, and PM3 vibrational frequencies indicate that only the decacation is a minimum on the potential energy hypersurface whereas the other two cations have many imaginary frequencies for non-totally symmetrical modes.