The role of the C₂ gas in the emergence of C₆₀ from the condensing carbon vapour

Abstract

A model has been developed that illustrates C₆₀’s emergence from the condensing carbon vapour. It is shown to depend upon (i) the decreasing heats of formation for larger cages; (ii) exponentially increasing number of isomers for fullerenes that are larger than C₆₀; (iii) large cages’ buckling induced by the pentagon-related protrusions that initiate fragmentation; (iv) the structural instability-induced fragmentation that shrinks large cages via C _x → C _x−2 + C₂; and (v) an evolving gas of C₂ that is crucial to the whole process. The model describes a mechanism for the provision and presence of plenty of C₂s during the formation and fragmentation processes. Fullerenes portrayed as 3D rotors have partition functions describing ensemble’s entropy as a function of the fragmentation sequence. The bottom-up formations of large cages followed by the top-down cage shrinkage are shown to be stable, dynamical processes that lead to the C₆₀ dominated fullerene ensemble.