Investigation of the Effect of Atomic Structure Defects on the Thermal Expansion Coefficient of Zigzag and Armchair Carbon Nanotubes Using Molecular Dynamics Method

The mechanical and physical properties of carbon nanotubes depend on their size and atomic structure. Accurate determination of the properties of carbon nanotubes, including the coefficient of thermal expansion, has many practical problems due to the limitations of laboratory methods. In this study, molecular dynamics method has been used to investigate and extract the properties of thermal expansion coefficient in a number of samples of carbon nanotubes that have different diameters and armchair and zigzag structures. In this study, the effect of atomic structure defects including Stone–Wales and vacancy defects on the coefficient of thermal expansion and longitudinal elastic mechanical properties of carbon nanotubes have been investigated. The potential function used in COMPASS simulation. Based on the obtained results, the coefficient of thermal expansion for CNT (7,7) at a temperature of 800 K is calculated at about 6.34 , which shows a good agreement with the results of laboratory studies. Also, the presence of defects in the atomic structure, including the defect of the non-reconstructed vacancy, in most cases has increased the coefficient of thermal expansion, which has been equal to 65% in CNT (0, 7). The vacancy defect is more effective than the Stone-Walsh defect in changing the coefficient of thermal expansion. The results show that the elastic properties of the CNT case study are also weakened by 22% due to the defect of the vacancy in the longitudinal direction.