Theoretical studies on relative stabilities of C70 fullerene dimers

Five stable fullerene dimers (C70)2 with [2+2] bridges between hexagon-hexagon bonds, which are experimentally characterized very recently, have been investigated by several semi-empirical MO approaches and ab initio Hartree-Fock self-consistent field calculation and hybrid density functional theory treatment. Energy difference among the five isomers is predicted to be quite small, where two of them seem to be isoenergetic. The computed B3LYP/6-31G temperature-dependent relative concentrations indicate the two lower energy isomers to be the most thermodynamically populated one with a ratio of 1:1 over a wide temperature area. This finding agrees reasonably well with the recently reported experimental observations