STRUCTURAL DEFECTS AND THE SHAPE OF LARGE FULLERENES

Motivated by the recent experimental observation of nearly spherical multi-layer fullerenes, we investigate theoretically the role of thermally generated structural defects on the shape and stability of large fullerenes by equilibrium statistical mechanics methods. Low energy defects are generated via atom insertions and bond rotations and the resulting structures are relaxed using realistic atomic potentials. The lowest defect formation energies are about 1 eV. A free energy analysis shows that large fullerenes will contain a substantial number of such defects at high temperatures. The presence of these defects effectively spreads out the sharp ''kinks'' associated with the faceted ground state structure, leading to a more spherical cage of a uniform curvature.