CALCULATIONS ON THE ELECTRONIC-STRUCTURE AND SPECTROSCOPY OF C-60 AND C-70 CAGE STRUCTURES

A study of the electronic structure and spectroscopy of models of C60 and C70 cage structures has been carried out using the intermediate neglect of differential overlap (INDO) model Hamiltonian. The geometry for these cages was obtained using gradient-driven methods, and at least in the case of C60, where information is available, is in good accord with the calculations of others. Using a small active space of only single excitations, both configuration interaction (CI) and random phase approximations (RPA) yield spectra in excellent agreement with that obtained from recent experiments. The oscillator strength of the band calculated at approximately 47000 cm-1, however, dramatically diminishes as the active space is increased, even though the sum rule increases. We discuss this interesting observation as well as the calculated structure and spectrum of C70.