Electronic structure and optical properties of bare and coated C60 molecules

Ground state electronic structures of C60 and metal coated C60, modeled with the clusters Li12C60 and Li32C60, are analyzed within the local density functional approximation. The low-energy part of the linear-response spectra of a bare C60, Li12C60 and Li32C60 is also studied. The Kohn-Sham molecular wavefunctions are used for the evaluation of dipole matrix elements and polarizabilities, and the effect of screening the oscillator strengths is found using a simplified RPA approach. For the Li-coated C60 species the electronic level diagram shows correspondence to the C60 level diagram but with new levels originating from Li close to the Fermi level. New structure in the oscillator strength distribution from the Li-coating is found at lower energy than the π plasmon of C60 at about 6 eV.