Rehybridization and pi-orbital alignment: The key to the existence of spheroidal carbon clusters.

Carbon clusters have been the focus of many experimental studies using a variety of techniques. Recently, Smalley and coworkers have proposed novel 3-dimensional spheroidal or ellipsoidal structures for even-numbered carbon clusters containing 40- 80 atoms. In particular, they have suggested a highly symmetric truncated icosahedral structure ("soccer ball" like) for C (60). In this work, we have investigated the nature of the bonding and resonance stabilization involved in such hollow spheroidal structures. The rehybridization necessary to form these structures has been analyzed in terms of the recently developed pi-orbital axis vector (POAV) analysis. Larger clusters are shown to be favored and the lower critical value of n to form stable spheroidal C(n) is discussed.