K. Raghavachari et Cm. Rohlfing, ISOMERS OF C-78 - COMPETITION BETWEEN ELECTRONIC AND STERIC FACTORS, Chemical physics letters, 208(5-6), 1993, pp. 436-440
Ab initio Hartree-Fock (3-21G and 6-31G(5d)) calculations on the stru
ctures and stabilities of the low-energy isomers of C78 are reported.
The energy ordering of the isomers can be interpreted in terms of two
different physical effects: an electronic factor which maximizes the r
esonance stabilization energy and a steric factor which minimizes the
strain energy. The nature of the three most stable isomers (C2v, C2v',
and D3) seen in two different experiments can be understood in terms
of competition between these two opposing effects.