Semiempirical vibrational and electronic structures of C60 and C70

The electronic and vibrational structures of C60 and C70 have been calculated at the PM3 semiempirical level. C60 has a partially delocalized structure, while C70 has both a localized set and a delocalized set of MOs. As with AM1 and MNDO, PM3 predicts the heat of formation of C70 to be greater than that of C60, and that C70 is the thermodynamically more stable species. Calculation of the normal modes was accelerated over 40 times by limited use of symmetry theory.