Relative abundance of single and double vacancies in irradiated single-walled carbon nanotubes

Double and single vacancies differently affect the conductance of carbon nanotubes [G. Gómez-Navarro et al., Nat. Mater. 4, 534 (2005)], so that the exact knowledge of the abundance of these defects is mandatory for an unambiguous interpretation of irradiation-induced changes in nanotube conductance. We calculate concentrations of defects produced by Ar ions using the molecular dynamics method combined with kinetic Monte Carlo simulations. Carefully taking into account the annealing of defects, we show that the ratio of single to double vacancies has a minimum at ion energies of about $0.5keV$ and that the ratio saturates toward a constant value at high ion energies.