Effects of vacancy defect reconstruction on the elastic properties of carbon nanotubes

Taking typical armchair (5,5) and (10,10) single-walled carbon nanotubes (SWCNTs) as its study subjects, this study adopts the molecular dynamics method to investigate the vacancy defect reconstruction and elastic properties of these SWCNTs with different defect ratios. The results show that single vacancies and di-vacancies in SWCNTs have different reconstructions. A single vacancy reconstructs into a 5-1DB configuration when the temperature is about or higher than 2400 K, and a di-vacancy reconstructs into a 5-8-5 configuration when the temperature is about or higher than 2600 K. At room temperature, the Young's moduli of armchair (5,5) and (10,10) SWCNTs with no defects are 948 and 901 GPa, respectively. When the vacancy defect achieves a certain ratio, there is a sudden slow down in the curves of the Young's moduli versus the vacancy defect ratio and a platform phenomenon emerges. The reconstruction of vacancy defects can be carried out by way of not only temperature but also the defect ratios in SWCNTs because of the activity of dangling bonds and their spaces. Vacancy defects will bring about a decrease in the Young's modulus, but their reconstruction will be an important factor in stabilizing the modulus. (C) 2009 Elsevier Ltd. All rights reserved.