AN ANALYTICAL MODEL FOR SCREENED COULOMB INTERACTION IN A C-60 CLUSTER

An analytical model for the static screened Coulomb interaction of a s emiconductor sphere that accurately reproduces the screening propertie s of an icosahedral C-60 cluster is presented. Compared with the stati c screened Coulomb interaction determined after polarizability calcula tions it yields the same value for nearest-neighbor interaction energy and the same antiscreening effect for distant sites for points locate d on the nuclear grid of a free molecule. Also the static dipole molec ular polarizability turns out to be in good agreement with that calcul ated after different theoretical methods. When extended to finite freq uencies, without introducing other parameters, the present model repro duces the main resonance around 20 eV of the optical absorption spectr um for the gas phase C-60 and the giant plasmon resonance around 28 eV observed in C-60 fullerites via electron energy loss spectroscopy. Th ese results turn out to be largely insensitive to the details of the m odel.