First-principles total-energy electronic-structure calculations in density functional theory were performed for C nanotubes with a defect that consisted of a pair involving an adatom and a vacancy. It was found that the activation barriers for formation and healing of the defect were ≈10 and 2eV, respectively; thus indicating the possibility of defect-healing under moderate conditions. The defect was found to induce 2 gap states having characteristics that depended strongly upon its arrangement. The metal–insulator transition took place on the (9,0) nanotube; due to the formation of gap states.

Energetics and Electronic Structures of Carbon Nanotubes with Adatom–Vacancy Defects. S.Okada: Chemical Physics Letters, 2007, 447[4-6], 263-7