Atomistic Failure Mechanism of Single Wall Carbon Nanotubes with Small Diameters

Single wall carbon nanotubes with small diameters (<5.0Å) subjected to bending deformation are simulated by orthogonal tight-binding molecular dynamics approach. Based on the calculations of C--C bond stretching and breaking in the bending nanotubes, we elucidate the atomistic failure mechanisms of nanotube with small diameters. In the folding zone of bending nanotube, a large elongation of C--C bonds occurs, accounting for the superelastic behaviour. The C--C bonds parallel to the axis direction of nanotube are broken firstly due to the sustained longitudinal stretching strain, giving rising to forming one-notch or two-notch bond-breaking mode depending on nanotube chiralities. The direct bond-breaking mechanism is responsible for the brittle fracture behaviour of nanotubes with small diameters.