Molecular dynamics methods, involving a classical many-body potential and artificial dissipation of energy, was used to simulate the structure of a fullerene with defects. The behavior of an interstitial C atom was investigated. The positions were checked by placing the interstitial atom there and permitting the system to relax. The stable position for the interstitial atom was situated at a distance of 0.098nm from the cluster center, and the bond energy was equal to 0.26eV. Another stable position was found which was equivalent to the first one. It was also on the line which connected the cluster center to the pentagon face center, and had a similar bond energy. As the bond energy of an interstitial atom was not large at the final temperature, it could migrate from one stable position to another one. This was similar to the well-known caging effect of an impurity in a lattice of heavier atoms. In order to determine the migration energies, an atom in one of the equilibrium positions was given a certain speed in the direction of the neighboring stable position. The speed was gradually increased until the atom broke through the potential barrier. The migration energies were of the order of 0.2 to 0.3eV.

Fullerene Molecule Structure with an Interstitial. V.V.Kirsanov, I.Y.Yanov: Physics Letters A, 1994, 193, 188-90