A study was made of the effects of randomly distributed Stone–Wales defects on the mechanical properties of single-walled nanotubes using the technique of atomistic simulation. A Matern hard-core random field applied to a finite cylindrical surface was used to describe the spatial distribution of the Stone–Wales defects. Simulations were made of a set of displacement-controlled tensile loadings, up to fracture, of single-walled nanotubes with (6, 6) armchair and (10, 0) zig-zag configurations and an aspect ratio of about 6. A modified Morse potential was used to model the interatomic forces. It was found that fracture invariably initiated from a defect, if one was present. In a defect-free tube, the crack initiated at random locations. The force–displacement curve typically behaved almost linearly up to about half way, although there was no obvious yield point. The stiffness, ultimate strength and ultimate strain were calculated from the simulated force and displacement-time histories. A randomness in mechanical behaviour, resulting only from the initial velocity distribution, was found to be insignificant at room temperature. The mean values of stiffness, ultimate strength and ultimate strain of the tube decreased as the average number of defects increased; although the coefficients of variation did not exhibit such a monotonic trend. The introduction of an additional defect had the most pronounced effect upon the randomness in mechanical properties when the tube was originally defect-free. It was also found that, for a given mean number of defects in the tube, the zig-zag configuration tended to have a lower strength and ultimate strain, but exhibited more uncertainty in its stiffness and ultimate strain, when compared with the armchair tube.

Effect of Randomly Occurring Stone–Wales Defects on Mechanical Properties of Carbon Nanotubes using Atomistic Simulation. Q.Lu, B.Bhattacharya: Nanotechnology, 2005, 16[4], 555-66