A study of the isomers of C36 fullerene using single and multireference MP2 perturbation theory

The role of electron correlation in the five lowest energy isomers of C36 fullerene is studied using the CASSCF method with single and multireference MP2 theories. It is shown that the distortion of the D6h isomer at HF levels of theory is an artificial effect caused by the oversimplified form of the wavefunction. The singlet state of the D6h isomer has diradical character, and it is the lowest energy state. The triplet states of the D6h and D2d isomers are 34 and 92 kJ/mol and the singlet state of the D2d isomer is 148 kJ/mol higher in energy than the D6h singlet state.