We present follow-up studies on the formation mechanism of fullerene molecules from random ensembles of C2 molecules using quantum chemical molecular dynamics. Two possible roadmaps are investigated as to how buckminsterfullerene C60 and higher fullerenes could be formed. In a "size-up" scenario, fullerenes of the cage size of C72-C96 were found to form directly from high concentrations of C2 molecules at 2000 K with periodic supply of batches of additional C2's. In a "size-down" approach, smaller fullerenes are sometimes formed by losing carbon fragments in "fall-off" or "pop-out" annealing processes under prolonged heating of giant fullerenes, which were self-assembled at initial stages from C2's with lower concentrations. Both roadmaps are found to provide explanations for the appearance of C60 and larger fullerenes in combustion and carbon arc experiments.
(c) 2005 American Institute of Physics.