Nucleation and healing of structural defects in single-walled carbon nanotubes, studied using reactive molecular dynamics simulations and reactive molecular dynamics trajectories, revealed the formation and healing mechanisms of various topological defects on the catalyst surface. The quality percentage of nanotubes was measured by calculating the number of hexagons per carbon atom relative to the same quantity for a perfect nanotube of the same length. Following this approach, the concentration of defects was estimated for nanotubes grown on catalysts with different sizes and morphologies and for various temperatures and gas-phase densities. From this analysis, specific catalyst morphologies were identified that favored the growth of single-walled carbon nanotubes with low defect concentration. Vacancies, 5-7, and Stone-Wales defects were observed to nucleate distinctly in the tubes depending upon the catalyst morphology. It was found that a strong interaction between the catalyst surface and the graphitic lattice of the nanotube was absolutely necessary for the healing and formation of defects. The study suggested that defects could be healed independently of the degree of embedding of the defective structure into the tube structure. Diffusion and catalytic events at the catalyst/tube interface were the main sources of nanotube structural recovery on the catalyst surface. Optimal growth conditions were identified that allowed significant structural healing in nanotubes.

Dynamics of Topological Defects in Single-Walled Carbon Nanotubes during Catalytic Growth. J.C.Burgos, E.Jones, P.B.Balbuena: Journal of Physical Chemistry C, 2014, 118[9], 4808-17