Radial Stability And Configuration Transition Of Normal And Abnormal Carbon Nanotubes

Carbon nanotubes (CNTs) have attracted much attention in the past two decades due to their superior mechanical, electrical and chemical properties. Especially owing to their hollow structures and smooth surfaces, CNTs are promising as ideal carriers and storages for drug, fluid, low-dimensional nanomaterial, etc, and have shown great potential applications in many fields, such as nanomedicine and nanoelectronics. However, the functionalities and performances of CNT-based devices and systems are closely related to the radial stability of the CNTs. Thus, it is of great importance to understand the radial stability of CNTs with different sizes and chiralities from experimental, theoretical and simulation aspects. In the present work, the radial stability and configuration transition of conventional or abnormal CNTs have been studied by using atomistic simulations.The radial stability and configuration transition of conventional single-, double-and triple-walled CNTs have been firstly studied. The equilibrium configurations of open and collapsed CNTs have been obtained by using molecular mechanics simulations. Then the Nudged Elastic Band (NEB) method has been adopted to determine the transition from open to collapsed configurations and the corresponding activation energy. The effects of radius and chirality on the collapse behaviors of CNTs have been analyzed. Major findings are:1) The activation energy for the collapse of CNTs decreases with increasing the radius of the CNTs and CNTs with a large radius can collapse easier.2) The activation energy of armchair CNTs is a little higher than that of zigzag CNTs with the same radius.3) The activation energy increases with the increase of the wall numbers.Then the radial stability and configuration transition of abnormal double-and triple-walled CNTs have been studied. The equilibrium configurations of open abnormal CNTs have been constructed according to previous works. Then the collapsed configurations have been obtained by using molecular mechanics method. Then the NEB method has been used to determine the activation energy for the collapse of abnormal CNTs. Major findings are:1) When the radius of the inner CNTs is small, the inner CNTs do not collapse and mainly act as defects, thus the activation energy decreases with the increase of the inner radius.2) With further increasing the radius of the inner CNTs, the inner CNTs become supporters that can enhance the radial stability of the abnormal CNTs and thus the activation energy increases.