Accurate Thermochemical and Kinetic Stabilities of C₈₄ Isomers

Accurate double-hybrid density functional theory and isodesmic-type reaction schemes are utilized to report accurate estimates of the heats of formation (Δ_f H) for all 24 isolated-pentagon-rule isomers of the third most abundant fullerene, C₈₄. Kinetic stabilities of these C₈₄ isomers are also considered via C-C bond cleavage rates ( P_cleav) calculated using density functional theory. Our results show that the relative abundance of C₈₄ fullerene isomers observed in arc discharge synthesis is the result of both thermochemical and kinetic factors. This provides timely insight regarding the characterization of several C₈₄ isomers that have been obtained experimentally to date. For instance, the established assignments of C₈₄ isomers of (using the Fowler-Manolopoulos numbering scheme) 22 [ D₂(IV)], 23 [ D_{2 d}(II)], 19 [ D_{3 d}], 24 [ D_{6 h}], 11 [ C₂(IV)], and 4 [ D_{2 d}(I)] are consistent with the relative Δ_f H and P_cleav values for these structures. However, our thermochemical and kinetic stabilities of C _s isomers 14, 15, and 16 indicate that the two experimentally isolated C _s isomers are 15 and 16, contrary to some previous assignments. Of the remaining isolated isomers of symmetry C₂ and D₂, definitive assignment was not possible with consideration of only Δ_f H and P_cleav.