Fullerene cage clusters. The key to the structure of solid carbon

Abstract

The recent plethora of carbon cluster studies has yielded results which indicate that several different types of intermediate participate in the formation of carbon microparticles in the gas phase. Cumulene and/or poly-yne chains, either open-ended or in the form of monocyclic rings occur. It has been proposed that some of the more stable clusters are closed-cage fullerenes (C₆₀buckminsterfullerene being archetypal) and other which are highly reactive have curved and closing shells. These may be the embryos which accrete carbon rapidly, ultimately resulting in carbon microparticles. The nucleation mechanism developed to explain the spontaneous formation of C₆₀ predicts that such microparticles should have icospiral concentric shell internal structures, a result which can be shown to be quantitatively consistent with observation. This analysis and the relationships between the various carbon clusters are surveyed here. There are several important aspects of this new nucleation scenario that suggest that it applies to soot formation as well.