Energetics of Stone-Wales defects in 4 A carbon nanotubes

Density functional calculations have been performed to study the formation of Stone-Wales defects in 4 A single-wall carbon nanotubes, which were firstly synthesized inside the AFI zeolite template. The minimum energy paths from perfect tubes to defect-containing ones are calculated by the nudged elastic band method. It is found that the C--C bonds "along" the tube axis are more likely to be rotated than those bonds "around" the circumference. There is a marked chirality dependence of the formation barriers, which are found to be lower than that of graphite. Our results may raise a question on the origin of superconductivity observed in these 4 A tubes.