SCREENING EFFECTS IN C-60 SOLIDS

The dielectric function for solid C-60 is calculated within local-dens ity-functional theory. The screened Coulomb interaction shows a remark able orientation and position dependence. Inter-molecular screening is stronger than intra-molecular screening and screening increases with inter-molecular separation. Some of the inequivalent on-site atomic sc reened Coulomb integrals are comparable to the nearest-neighbour terms and tbe second-nearest-neighbour terms are smaller than the third-nea rest-neighbour terms. The screened on-site molecular Coulomb integral U-0 is found to be similar to 2.1 eV and the local multiplet splitting for three electrons in the t(1u) is similar to 0.12 eV, suggesting th at electrons in the derived band should be highly correlated.