Reconstruction properties of a single vacancy in zigzag carbon nanotubes and their effects on elastic properties

The molecular dynamics method is adopted in this paper to investigate single vacancy defect reconstruction in zigzag single-walled carbon nanotubes (SWCNTs) at different temperatures, and the effects of the defect ratio on their elastic properties. The results show that there are two types of reconstruction in zigzag (9, 0) SWCNTs. A single vacancy begins to reconstruct into a 5-1DB-P configuration when the temperature is about or higher than 1600 K, and a 5-1DB-T configuration at about or higher than 2600 K. However, these reconstructions do not always take place at these temperatures, i.e., the reconstruction temperatures are discrete. For this reason, a new idea has been put forward: that there are two sets of noncontinuous potential barriers between the three dangling bond (3DB) states and the reconstructions, which correspond to the 5-1DB-P and 5-1DB-T barriers. The Young's moduli decreased with the increase of the single vacancy defect ratio in these SWCNTs, and the decreasing speed suddenly decelerates at a certain vacancy defect ratio, i.e., a platform phenomenon emerges. Based on the above results, it can be concluded that the vacancy defects can be reconstructed not only by way of temperature, but also by the defect ratios in SWCNTs. Copyright © 2009 American Scientific Publishers All rights reserved.