ISOMERS OF C-20 - DRAMATIC EFFECT OF GRADIENT CORRECTIONS IN DENSITY-FUNCTIONAL THEORY

Density functional techniques including gradient corrections are used to investigate the relative energies of the ring, bowl (corannulene-li ke), and cage (fullerene-like) isomers of C20. In agreement with previ ous studies, the local density approximation yields the cage to be the most stable isomer with the bowl and ring forms being significantly h igher in energy. However, the inclusion of gradient corrections comple tely reverses the energy ordering of the isomers. The gradient correct ion alters the relative energy between the cage and ring isomers by mo re than 7 eV and yields the ring as the most stable form.