C_(98) IPR isomers: Gibbs-energy based relative stabilities

摘要

The complete set of 259 isolated-pentagon-rule (IPR) isomers of C_(98) has been treated by full geometry optimizations with the SAM1, PM3, AM1, and MNDO quantum-chemical semi-empirical methods. All the applied methods point out a C_2 species (FM code, 248:C_2) as the lowest-energy structure in the IPR set. In order to predict the relative stabilities at elevated temperatures, entropy contributions are also computed and thus, evaluations in terms of the Gibbs energy are possible for this system for the first time. Interesting stability interchanges in the isomeric set are found so that not only the ground-state structure 248:C_2 but also other structures (109:C_1, 108:C_s, 113:C_2) are significantly populated at high temperatures. The results are placed into a wider context of higher fullerenes and their computations.