Theoretical study of position-dependent defect formation in a   single-walled carbon nanotube: Stability towards an open end
  Point defects, including atom vacancy, add atom and Stone-Wale defect, close to a (5, 5) single-walled carbon nanotube (SWNT) end were studied by DFT, semi-empirical PM3 method and empirical Brenner Potential. It is found that closer to the SWNT opening end more stable these defects are. Based on these calculations, a model about fixing defects on a growing SWNT by defects diffusing to the SWNT opening end was proposed. Furthermore, calculations also show that, similar to the DFT calculation, semi-empirical PM3 method is accurate enough for studying defect formation in SWNT. In contrast, the results based on the empirical Brenner potential show large errors and sometimes even not correct in quality. 
Feng Ding