CANONICAL STRUCTURE OF LARGE CARBON CLUSTERS - CN, N-GREATER-THAN-100

We present direct imaging of carbon clusters using high-resolution electron microscopy. We find the stable form of carbon particles, obtained after electron irradiation, to be a spherical, concentric-shelled graphitic structure, rather than a hollow cage, icosahedral or tubular. The shells of these onionlike particles are remarkably well crystallized. They are stable under an intense electron beam, even when formed of only a few shells (2 divided-by 5). We suggest that the canonical form of large carbon clusters, containing more than a hundred atoms, is the spheroidal, concentric-shelled graphitic structure.