C20: Fulleren, Bowl or Ring? New Results from Coupled-Cluster Calculations

Contrary to recent experimental evidence suggesting that the monocyclic ring is the most stable 20-atom carbon species, highly accurate calculations convincingly predict that the smallest fullerene, the dodecahedron C${}_{20}$, has the lowest energy. A related corannulene-like bowl is nearly degenerate in energy to the fullerene. Thermodynamic considerations suggest that at formation temperatures of around 700 K the bowl should be the dominant species. The recent application of gradient corrections to LDA which supported the ring structure is qualitatively in error. (RK-94-02)