THE CHARGE STATE OF C-60 (BUCKMINSTERFULLERENE) MOLECULES ADSORBED ON A METAL-SURFACE - THEORETICAL CONSIDERATIONS

The charge state of a C60 molecule is strongly dependent on its environment. We discuss the factors that determine the charge state of C60 molecules adsorbed on metal substrates. An estimate of the charge state of a C60 molecule adsorbed without covalent bonding on a smooth simple metal surface is calculated taking into account the Coulomb interaction of the C60-n ion with its image charge and the polarization of the molecule, assuming the metal to be a perfect conductor, and the van der Waals interaction, using a Lennard-Jones pairwise potential based on graphite. We find that at most two electrons can be transferred to the molecule regardless of the work function of the metal. The broadening of the LUMO level of the adsorbed molecule due to resonance with the substrate energy levels will allow for a partial charge transfer even for metal substrates with work functions as high as 4.5 eV.