Fig. 1.
An axial screw dislocation in the CNT. An achiral zigzag (n, 0) tube (A) can be viewed as a perfect crystal, and transformed into a chiral one by cutting, shifting by a Burgers vector b (red arrows in B–D), and resealing a tube-cylinder (B). The chiral (n, 1) in (C) and (n, 2) in (D) tubes contain the axial screw dislocations with a single and double value of bγ, accordingly; the corresponding kinks at the open tube-end are marked in red. (E) Free energy profile during the growth of a chiral or achiral nanotube.