A first-principles pseudopotential method was developed for calculating the quantum conductance as well as the self-consistent charge distributions of nanostructures and the electronic structure and quantum conductance of carbon nanotubes with impurities or defects. Even if the carbon nanotube was metallic instead of semiconducting, boron and nitrogen atoms created acceptor-like and donor-like states which acted as scattering centers for conducting electrons. Various defect geometries such as Stone-Wales defects were considered which gave rise to interesting localized states and conductance characteristics. The localized states were in resonance with the extended states of the metallic nanotube and formed quasi-bound states having broadened energy levels, leading to novel conductance behaviors. For semiconducting carbon nanotubes, it was shown that various defects located at the junction of two different nanotubes could produce both shallow and deep defect levels.

Electronic Structure of Defects and Quantum Transport in Carbon Nanotubes. J.H.Eom, H.Lee, J.Im, C.Park, B.Wook Jeong, S.Kim, J.Ihm: Physica B, 2006, 376-377[1], 7-10