First Principle Study of Electron Transport in Single-Walled Carbon   Nanotubes of 2 to 22 nm in Length
  An elongation method based on ab initio quantum chemistry approaches is presented. It allows to study electronic structures and coherent electron transportation properties of single-walled carbon nanotubes (SWCNTs) up to 22nm in length using the hybrid density functional theory. The 22nm long SWCNT, consisting of more than ten thousands electrons, is the largest carbon nanotube that has ever been studied at such a sophisticated all-electron level. Interesting oscillating behaviour of the energy gap with respect to the length of the nanotube is revealed. The calculated current-voltage characteristics of SWCNTs are in excellent agreement with recent experimental results. It confirms the experimental observation that a 15nm long SWCNT is still largely a ballistic transport device. The proposed elongation method opens up a new door for the first principle study of nano- and bio-electronics. 
Jun Jiang, Wei Lu and Yi Luo