Energetic analysis of pentagon road intermediates of C-60-buckminsterfullerene formation

We report an energetic analysis of the principal intermediates of the pentagon road (PR) scheme for formation of C-60-buckminsterfullerene. All calculations were initially performed using the tight-binding semiempirical method. For selected cases, more rigorous 3-21G/HF and 3-21G/B3LYP calculations were carried out. The first part of this study includes an energetic comparison between the 30-, 40-, and 50-atom PR intermediates and a representative group of 30-, 40-, and 50-atom carbon clusters. While C-30 PR is higher in energy than a large variety of graphene sheets and fullerenes, C-40 PR and C-50 PR are considerably lower in energy than many other isomers; only fullerenes are more stable. Additionally, we examine a plausible mechanism by which C-50 PR rearranges to form a C-50 cage with D-5h symmetry. Because of its large energy barrier, this process is unlikely to affect the C-60 growth mechanism.