Catalysis of nanotube plasticity under tensile strain

We have performed ab initio simulations to investigate the effect of carbon adatoms on the plastic deformation of carbon nanotubes. Under applied stress, the system spontaneously undergoes a Stone-Wales transformation catalyzed by the exchange of the adatom with a substrate atom. The unraveled mechanism reduces the barrier by a factor 3 to 5 and is the same as the one recently proposed by Ewels [Chem. Phys. Lett. 351, 178 (2002)] for C-60. The activation energies for such a transformation in graphene and nanotube systems under various stresses are obtained within an ab initio nudged elastic band approach. The catalytic action is enhanced when the carbon adatom is replaced by boron.