Mechanism of strain release in carbon nanotubes

Static and dynamical properties of carbon nanotubes under uniaxial tension have been investigated via quantum and classical simulations. In strained nanotubes at high temperatures we observe the spontaneous formation of double pentagon-heptagon defect pairs. Tubes containing these defects are energetically preferred to uniformly stretched tubes at strains greater than 5%. These topological defects act as nucleation centers for the formation of dislocations in the originally ideal graphite network, and they constitute the onset of a plastic deformation of the carbon nanotube. The mechanism of formation of such defects, their energetics, and transformations are described.