Defect Healing during Single-Walled Carbon Nanotube Growth: A Density-Functional Tight-Binding Molecular Dynamics Investigation

Abstract

Quantum chemical molecular dynamics have been employed to investigate the healing of single-walled carbon nanotubes (SWNTs) during growth. In trajectories based on self-consistent-charge density-functional tight-binding (SCC-DFTB) energies and gradients, gas-phase carbon atoms were supplied to the carbon−iron boundary of a model C40-Fe38 complex at two different rates (1 C/0.5 ps and 1 C/10 ps). The lower rate of carbon supply was observed to promote SWNT growth, compared to the higher rate, for the same number of carbon atoms supplied. This promotion of growth was ascribed to the suppression of pentagon and heptagon incorporation in the sp2 carbon network observed at lower carbon supply rates. The most successful example of growth occurred when the respective periods of hexagon and pentagon formation were out of phase and heptagon formation was limited. Higher carbon supply rates tended to result in the encapsulation of the Fe38 cluster by the extended sp2 carbon cap, due to a saturation of pentagon and ...