Formation of ${\mathrm{C}}_{60}$ clusters via Langevin molecular dynamics

We examine the formation of ${\mathrm{C}}_{60}$ clusters via a Langevin molecular-dynamics simulation. Our simulation incorporates a carbon interatomic potential which reproduces correctly the binding energy and bond lengths of the stable carbon polymorphs. We find that it is possible to nucleate a ${\mathrm{C}}_{60}$ fullerenelike cluster with no symmetry, or volume imposed constraints from a ‘‘weakly’’ interacting ‘‘hot gas’’ of carbon atoms. We propose that the growth sequence for ${\mathrm{C}}_{60}$ fullerene in the initial phase is dominated by the nucleation of long carbon chains. As the nucleation process proceeds, these chains branch and form polycyclic rings. We find an abrupt onset of ring formation at a temperature which corresponds approximately to the melting point of graphite. Also, we propose an annealing technique that expedites the formation of stable clusters.