Defectdefect interaction in single-walled carbon nanotubes under torsional loading

This paper presents an analysis of interactions between a pair of StoneWales (SW) defects in a single-walled carbon nanotube (SWCNT) that has been subjected to an external torque. Defect pairs, representing the different combinations of SW defect of A (SW-A) and B (SW-B) modes, were incorporated in SWCNT models of different chirality and diameter and solved using molecular mechanics. Defectdefect interaction was investigated by evaluating the CC steric interactions in the defect that possesses the highest potential energy, E, as a function of inter-defect distance, D. This study reveals that the deformation of the CC bond is attributed to bond stretching and bending. In the SW-B defects, there is an additional contributor arising from the dihedral angular deformation. The magnitude of E depends on the type of defect but the profile of the E versus D curve depends on the orientation of the defects. The largest indifference length, D₀, beyond which two defects cease to interact, is approximately 30 Å. When the angular displacement of the tube increases two-fold, E increases, but the profile of the E versus D curve is not affected. The sense of rotation affects the magnitude of E but not the profile of the E versus D curve.