CLOSED-SHELL ELECTRONIC REQUIREMENTS FOR SMALL FULLERENE CAGE STRUCTURES

Huckel model calculations have been performed for small fullerene cages with 20-50 atoms. The closed-shell electronic structures for the small cages are emphasized. The relatively high stability of C-24, C-28, C-32, C-44 and C-50 clusters observed in the early laser vaporization experiments is explained. These clusters have pseudo closed-shell or half-filled electronic structures with a relatively large HOMO-LUMO gap. Based on the Huckel results, we propose a large number of other possible stable clusters formed by adding hydrogens, replacing carbons with other atoms which have an appropriate number of valence electrons, or encapsulating metal atoms capable of donating a given number of valence electrons.