It was noted that, although as-grown nanotubes had relatively few defects, defects could appear at the purification stage or be introduced by irradiation or chemical treatment. The defects, especially vacancies, gave also rise to a deterioration of the axial mechanical properties of nanotubes. By employing molecular dynamics simulations and continuum theory, a study was made of how the Young's modulus and tensile strength of nanotubes with vacancy-related defects depended upon the defect concentration and defect characteristics. An analytical expression was derived, with coefficients parametrized from atomistic computer simulations, which related the Young's modulus and defect density in C nanotubes. It was further shown that the tensile strength and critical strain of single-walled nanotubes decreased by nearly a factor of 2 if an unreconstructed vacancy was present. This deterioration in the mechanical characteristics was partly offset by the ability of nanotubes to heal vacancies in the atomic network by saturating dangling bonds.

Mechanical Properties of Carbon Nanotubes with Vacancies and Related Defects. M.Sammalkorpi, A.Krasheninnikov, A.Kuronen, K.Nordlund, K.Kaski: Physical Review B, 2004, 70[24], 245416 (8pp)