Quantum chemical density-functional theory calculations were carried out for the six isomers obtained by removing four adjacent atoms from C60. The most stable isomer consists of twelve 5-member and eighteen 6-member rings, indicating that the removal of some atoms from C60, which contained twelve 5-member rings and twenty 6-member rings, does not always generate larger holes. Each of the other five isomers contained at least one 4-member ring and one larger ring (7-, 8-, 9- or 10-member ring) besides the 5- and 6-member rings. All isomers have similar structures for singlet and triplet spin multiplicities but with different stabilities. The ground states for two of the isomers were triplets, whereas the ground states for the other isomers were singlets. Furthermore, a comparison between the various isomers allowed one to examine the effect of the structure on the stability of fullerene cages.

Quantum Chemical Density-Functional Theory Calculations of the Structures of Defect C60 with Four Vacancies. Y.H.Hu, E.Ruckenstein: Journal of Chemical Physics, 2004, 120[17], 7971-5