On defect interactions in axially loaded single-walled carbon nanotubes

Despite the unparalleled mechanical properties of carbon nanotubes (CNTs), experiments have revealed large scattering which could be attributed to structural defects. How two neighboring defects may interact and influence the mechanical properties of CNTs is still unclear. Here, interactions between a Stone-Wales (SW) defect pair in axially loaded single-walled carbon nanotubes (SWCNTs) are systematically studied using molecular mechanics. The defect-defect interaction is quantified by the bond with the highest energy, E, which varies in magnitude with respect to the interdefect distance, D. Defect pairs, corresponding to combinations of two types of SW defects (namely, the SW defect of A and B modes) with a different relative orientation angle, φ, embedded in SWCNTs of different size and chirality were studied. It is shown from the results that, in general, E varies according to defect pair, and converges to a constant at large D. It is found that the magnitude of E is regulated by the type of defect pair, and the profile of E vs D is modulated by φ. In addition, E is also influenced by the tube size and chirality. From all of the cases studied, the largest indifference length, D0, beyond which two neighboring defects do not feel the existence of each other, is found to be approximately 30 Å.