Structure of (q = 0, 1, 2) fullerenes relevant in C60 fragmentation

We have studied the geometry of nine structural isomers of the neutral, singly- and doubly-charged C56 fullerene using the Hartree–Fock method and density functional theory. The structural features of C56 isomers that can appear in the fragmentation of C60 have been evaluated. We have found that the most stable structures correspond to the four isomers containing four pentagon adjacencies in the cage structure. These four structures are nearly degenerate in energy (within 8 kcal/mol). We have also considered isomers with heptagons that can be generated directly by C2 extraction from C58 and which are connected through Stone–Wales transformations with the most stables ones.