AN ABINITIO STUDY OF THE C-76 FULLERENE ISOMERS

The two possible isolated-pentagon fullerene isomers of C76, a chiral D2 structure with a closed-shell electronic structure and a T(d) isomer with an open-shell electronic configuration, are investigated by employing the Hartree-Fock self-consistent field method with minimal and double-zeta quality basis sets. The T(d) structure has a partially filled HOMO and is subject to first-order Jahn-Teller distortion. We found a closed-shell 1A1 state in D2d symmetry to be the lowest energy state for the T(d) isomer. Nevertheless, the D2 isomer is found to be 43 kcal/mol more stable than the symmetry-lowered T(d) --> D2d isomer at the SCF level of theory with the double-zeta basis set. Equilibrium structures and ionization potentials for both isomers are also presented.