Formation of helicity in an armchair single-walled carbon nanotube during tensile loading

In previous molecular dynamics (MD) simulations of deformation behavior of carbon nanotubes (CNTs), displacement rates ranging from 5.0 × 10−3 to 8.0 × 10−4 nm/step were used. In this work, a slower displacement rate (1.4 × 10−5 nm/step) was used to investigate deformation behavior of CNTs under tensile loading. Interesting findings were obtained. For the armchair CNT, during loading shear deformation occurred to the lattices before rupture, causing bond-breaking and re-bonding to the original carbon rings, and leading to the formation of a helix to the armchair, which is equivalent to introducing a screw dislocation into the CNT with a Burgers vector equal to the spacing between the carbon rings. The helix spiraled and propagated along the CNT. For the zigzag CNT, observable necking was formed locally before rupture, but no helix was formed. The necking in the zigzag was found to be recoverable after the external strain was released.