Stability of multishell fullerenes

Abstract
We investigate the equilibrium geometry of very large carbon clusters with special emphasis on nested multishell fullerene derivatives of spherical, cylindrical, and conic shape. For cluster sizes above 20 atoms, we find spherical shapes to be most stable. For very large sizes, a transition from single-shell fullerenes to multishell structures, locally similar to graphite, is energetically favored by the weakly attractive interaction between the shells.