Stone-Wales transformations triggered by intrinsic localized modes in carbon nanotubes

The crucial role of intrinsic localized modes (ILMs) in the atomic scale as a trigger of defect nucleation was studied using molecular-dynamics simulations for a (5,5) armchair carbon nanotube (CNT) under axial tension. A localized vibration at a pair of neighboring atoms was found to be the ILM, which simultaneously produces an intense concentration of kinetic energy, even in the structurally homogeneous CNT. The excited ILM was gradually amplified by the nonlinearity of C-C interaction. The amplified ILM, then, drove the breaking of the on-site C-C bond, which leads to the Stone-Wales transformation producing a topological defect consisting of two pentagons and two heptagons coupled in pairs. This signifies that mechanical instability can be activated by the ILMs. Such mechanism is expected to apply to other mechanical instabilities, e.g., as an origin of phase transformations in silicon under hydrostatic pressure.