Isomers of C24. Density functional studies including gradient corrections

Density functional techniques are used to investigate the relative energies of seven different structural isomers of C₂₄. The traditional local density approximation yields the fullerene-like isomer to be the most stable. As in the case of C₂₀, the inclusion of gradient corrections has a dramatic effect on the relative energies. The gradient-corrected B-LYP method yields the monocyclic ring and graphite-like isomers to be almost isoenergetic (and most stable) while the bicyclic ring, fullerene-like, and bowl-like isomers are progressively higher in energy. The Hartree—Fock results are quite similar to the B-LYP results. Implications to fullerene growth mechanisms are pointed out.