Bond lengths and reorganization energies in fullerenes and their ions

A very simple tight binding method with bond-length-dependent couplings, similar to the Su-Schrieffer-Heeger model. is described and applied to fullerenes in different charge states. The bond lengths, calculated from the pi bond orders. are in good agreement with results obtained by ab initio methods which include correlation, where comparisons can be made. The Jahn-Teller distortions are found to be small for the examples C-20 C-28-T-d, and C-60-I-h. Often many possible distortions are found. for example two different D-5d distortions for the C-20 spin triplet state. Bond reorganization energies (lambda(b)) for reduction and oxidation, which are measures for trapping efficiency and vibronic coupling, are obtained using a parabolic approximation of the energy surface.