Curvature effect on surface diffusion: The nanotube

Using an empirical Tersoff-Brenner many-body potential for the carbon atoms and a model Lennard-Jones interaction between the adatom and carbon atoms, the diffusion of an adatom over curved surfaces of C nanotubes is studied by calculating the potential energy surface and performing molecular dynami cs simulation. The average curvature of the surface is found to have an imp ortant influence on the diffusion of the adatom. Positive curvature increas es the diffusion barrier and corrugates the potential energy surface, while the negative curvature smoothes the potential energy surface, therefore it lowers the diffusion barrier. We also find that nanotube helicity can play an important role on the diffusion path, thus the adatom has different dif fusion path for the armchair and zig-zag nanotube. The nature of the curvat ure effect on the surface diffusion is connected with the strain effect. (C ) 2001 American Institute of Physics.