Vacancies in carbon nanotubes usually aggregate into larger vacancies. Using first-principles and tight-binding calculations, an investigation was made of the alignment of missing atoms and the movement of pentagon-heptagon defects that were formed by reconstructions in large vacancy clusters Vn (n ≤ 36), where n was the number of missing atoms. In nanotubes with small diameters, missing atoms had a tendency to form a serial network rather than a large hole due to the existence of large curvatures. It was generally found that the parallel alignment of missing atoms along the tube axis was energetically more favorable than a spiral alignment. Thus, the removal of atoms led to the longitudinal movement of a pentagon-heptagon defect on the tube wall, which was in good agreement with the kink motion observed during superplastic deformation of single-wall nanotubes. The preference of the longitudinal motion of the pentagon-heptagon defect was more prominent in armchair tubes compared with other chiral tubes.

Reconstruction and Alignment of Vacancies in Carbon Nanotubes. A.T.Lee, Y.J.Kang, K.J.Chang, I.H.Lee: Physical Review B, 2009, 79[17], 174105