Relative stabilities of C60H36 isomers are evaluated using both enthalpy and entropy terms, i.e., the Gibbs energy. The set consists of eight low energy isomers known from previous calculations and a new C-1 species, topologically equivalent to the recently isolated C-1 isomer of C60F36. The PM3 and B3LYP/6-31G* methods are applied, and in both treatments the new C-1 species is located 7 kcal/mol below the previous best C-1 structure. The treatments differ in the lowest energy isomer but they place the new C-1 isomer as the second most populated species at higher temperatures owing to its entropy enhancement. (C) 2003 Elsevier B.V. All rights reserved.