ELECTRONIC-STRUCTURES OF C28H4 AND HF-AT-C28H4 AND THEIR IONS - SCF CALCULATIONS

Ab initio restricted Hartree-Fock calculations were performed on the g round and excited states of C28H4, Hf@C28H4, and their positive and ne gative ions. Relativistic core potentials were included in the calcula tions to take account of the relativistic effects of the heavy atom. S ymmetry-adapted functions were used to reduce the time and effort of t he computation. Ionization potentials, electron affinities, MO interac tion diagrams, and population analyses of the systems were obtained. T hese results and those from our previous studies of Hf@C-28 were used to interpret the mode of bonding in C28H4 and Hf@C28H4, the mutual wea kening of the bonding of Hf and 4H to C-28, and the factors that affec t the bonding. These results can also shed light on the characteristic s of the bonding of endohedral and exohedral complexes of fullerenes i n general.