The Molecular Dynamics Study on Toroidal Carbon Nanotube and Carbon Nanospring

• Main Authors: Tzu-wen Chou, 周子文
• Other Authors: I-Ling Chang
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/66478863390157751539

碩士 === 國立中正大學 === 機械工程所 === 98 === In this study, the existence condition of perfect carbon toroidal ring without buckling and the elastic properties of carbon nanospring were investigated respectively using molecular dynamics simulation. The atomic model of toroidal ring is constructed by connecting both ends of the straight carbon nanotube. From the simulation results, it is noticed that for each nanotube radius, there exist a critical ring diameter, beyond which the toroidal ring could remain circular shape and the ring surface is smooth without bucklings. It is observed that the critical ring diameter increases as the nanotube radius increases and one empirical relation between the critical ring diameter and nanotube radius has been deduced. Besides, the strain energy of bending the straight beam with round cross-section into circular ring is calculated based on continuum theory and compared with the simulation results in order to examine whether the classical theory could apply in nanoscale. The atomic model of polygonal carbon nanospring is formed by joining both armchair and zigzag nanotube with similar radius. The topological pentagon-heptagon defects exist in the atomic model so that curvature configuration could remain stably. The effects of geometric sizes, i.e., the nanotube diameter, pitch and spring diameter, on the elastic properties of the nanosprings are systematically investigated. It is observed that as the tube diameter and pitch angle increases, the spring constant would increase. Moreover, the spring constant would decrease as the spring diameter and number of turns increase. Also, the spring constants predicted by the continuum spring model are compared with the simulation results and it is concluded that the predictions are in reasonably good agreement with the simulated spring constant of the polygonal carbon nanospring.