Towards formation of buckminsterfullerene C ₆₀ in quantum chemical molecular dynamics

We present follow-up studies on the formation mechanism of fullerene molecules from random ensembles of C ₂ molecules using quantum chemical molecular dynamics. Two possible roadmaps are investigated as to how buckminsterfullerene C ₆₀ and higher fullerenes could be formed. In a "size-up" scenario, fullerenes of the cage size of C ₇₂-C ₉₆ were found to form directly from high concentrations of C ₂ molecules at 2000 K with periodic supply of batches of additional C ₂'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 C ₂'s with lower concentrations. Both roadmaps are found to provide explanations for the appearance of C ₆₀ and larger fullerenes in combustion and carbon arc experiments.