Electronic properties of bromine-doped carbon nanotubes

Intercalation of bromine molecules (Br-2) into single-wall carbon nanotube (SWNT) ropes is studied using the ab initio pseudopotential density functional method. Electronic and vibrational properties of the SWNT and Br-2 are studied for various bromine concentrations. A drastic change in the charge transfer, bromine stretching-mode, and bromine bond-length is observed when the bromine-bromine distance decreases. Calculated electronic structures show that, at high bromine concentrations, the bromine ppsigma* level broadens due to the interbromine interaction. These states overlap with the electronic bands of the SWNT near the Fermi level which results in a substantial charge transfer from carbon to bromine. (C) 2002 Elsevier Science Ltd. All rights reserved.