Point defects, including atom vacancies, adatom, and Stone-Wale defects, close to a (5,5) single-walled C nanotube open end were studied by density functional theory, semi-empirical PM3 methods, and the empirical Brenner potential. It was found that defect stability increased as they became closer to the single-wall C nanotube open end. Based upon these results, a model for removing defects in a growing single-wall C nanotube was proposed, where the defects diffused to the single-wall C nanotube end. Furthermore, the calculations showed that the semi-empirical PM3 method compared well with density functional theory results, and was accurate enough for studying defect formation in single-wall C nanotubes. In contrast, the empirical Brenner potential yielded large errors and was sometimes not even qualitatively correct.

Theoretical Study of the Stability of Defects in Single-Walled Carbon Nanotubes as a Function of Their Distance from the Nanotube End. F.Ding: Physical Review B, 2005, 72[24], 245409 (7pp)