C72 isomers: the IPR-satisfying cage is disfavored by both energy and entropy

Relative concentrations of seven isomeric C72 cages (one species with isolated pentagons, two isomers with a pentagon–pentagon junction, a cage with a heptagon, a cage with two heptagons, and two isomers each with two pentagon–pentagon fusions) are computed using the Gibbs energy in a broad temperature interval. It is shown that the non-IPR C2v cage with one pentagon–pentagon junction prevails at any relevant temperature. Although the IPR-satisfying structure is the second lowest in energy, it is disfavored by entropy so that several cages still higher in energy are in fact more populated at higher temperatures.