  The electronic and structural properties of zigzag and armchair single-wall
carbon nanotubes (SWCNT) with a single vacancy or two vacancies located at
various distances have been obtained within the frame of the Density Function
Theory (DFT) and a Molecular Dynamics method. It is found that the vacancy
defects interact at long ranges in armchair SWCNTs unlike the short-range
interaction in zigzag SWCNTs. The density of states for different vacancy
densities shows that the local energy gap shrinks with the vacancy density
increase. This and other results of the investigation provide insight into
understanding the relation between the local deformation of a defective
nanotube and its measurable electronic properties.
