An ideal single vacancy could be formed by removing one C atom from a hexagonal network. The vacancy was one of the most important defect structures in C nanotubes. Vacancies could affect the mechanical, chemical, and electronic properties of C nanotubes. A systematic investigation was made of single vacancies and their related point defects for achiral single-walled C nanotubes by using first-principles calculations. The structures around single vacancies underwent reconstruction without constraint; forming ground-state or metastable-state structures. The 5-1DB and 3DB point defects could be formed in armchair C nanotubes, while the 5-1DB-P and 5-1DB-T point defects could be formed in zig-zag C nanotubes. The related point defects could transform into each other under certain conditions. The formation energies of armchair C nanotubes changed smoothly with the tube radius while, in the case of the 3DB defect, the formation energies tended towards a constant value as the radius became larger.

Geometry and Electronic Properties of Single Vacancies in Achiral Carbon Nanotubes. C.Wang, C.Y.Wang: The European Physical Journal B, 2006, 54[2], 243-7