It was noted that, although as-grown carbon nanotubes had relatively few defects, such defects could appear at the purification stage or could be deliberately introduced by irradiation with energetic particles or by chemical treatment. The defects, especially vacancies, also gave rise to a deleterious effect: deterioration of the axial mechanical properties of nanotubes. By using molecular dynamics simulations and continuum theory, it was shown how the Young’s modulus and tensile strength of nanotubes with vacancy-related defects depended upon the concentration of defects and their characteristics. An analytical expression was derived, with coefficients parametrized using atomistic computer simulations, which related the Young’s modulus and defect density in carbon 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 of the mechanical characteristics was partly alleviated 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], 1-8