Abstract
This article focuses on the analysis of cross-sectional deformations for single- and multi-walled carbon nanotubes using a molecular dynamics method. Carbon nanotubes consist of a graphene sheet (two-dimensional hexagonal lattices of carbon atoms) rolled up into a cylinder. This nanoscale structure has generated enormous interest in the research field of science and engineering in the last decades because of its excellent mechanical properties, such as extremely high elastic modulus and tensile strength. For example, the Young's modulus of nanotubes is estimated to be on the order of TPa (i.e., several times stiffer than steel) and the tensile strength is as high as tens of GPa. On the other hand, carbon nanotubes are known to have its remarkable flexibility when subjected to external hydrostatic pressure and bending force. Owing to such mechanical properties, they are regarded as an ideal material for superstrong nanofiber and thus hold great promise for use as next-generation materials. It has also been broadly accepted that mechanical deformation of a carbon nanotube causes significant changes in its physical and chemical properties. Precise knowledge of its deformation mechanism and available geometry is, therefore, crucial for understanding the precise physics and in developing nanotube-based applications. In earlier work, we carried out simulations based on the thin cylindrical shell theory to predict the occurrence of wavy-shaped carbon nanotubes, called “radial corrugation”. However, the shell theory is valid only within linear elastic region, thus being unavailing for discussing large deformation behaviours beyond elastic approximation. Against the backdrop, we have performed molecular dynamics simulations to explore the post-buckled behavior in the cross-section of carbon nanotubes under high pressure. We have confirmed various deformation modes with large amplitude, in which the stable mode is strongly dependent on the tube diameter and the number of concentric walls.
