Density functional theory (DFT) calculations show that the C-2-fragmentation of C-70 destroys 4 of 37 original rings and generates 3 new rings, leading to 8 possible isomers. Each of those isomers contains a larger ring (7-or 8-member ring) with or without 4-member ring(s) besides 5-and 6-member rings. The most stable isomer consists of thirteen 5-member, twenty-two 6-member, and a 7-member rings without 4-and 8-member rings. The C2-fragmentation energies (10.7-13.3 eV) of C-70 depend on resulted isomerstructures. Furthermore, the equilibrium fraction of the most stable isomer in the total isomers is 99.1%, 94.8%, and 94.0% at temperatures of 900, 1400, and 2000 K, respectively. (c) 2008 Elsevier B. V. All rights reserved.