First-principles study of carbon nanotubes with bamboo-shape and pentagon-pentagon fusion defects.

A first-principles study of single-walled carbon nanotubes with bamboo-shape (BS) and pentagon-pentagon fusion defects was conducted. Sharp resonances occur on the BS-nanotubes as strong density of electronic states (DOS) localized at carbon atoms adjacent to the partitions, while at the partition the localized DOS was greatly depleted. A strong defect state at -0.1 eV below the Fermi level was generated and the band gap was narrowed for BS-(10, 0) nanotube. Sharp resonant states are observed in the valence and conduction bands of BS-(12, 0) nanotube. The resonant states are attributed to the pentagon defects as exemplified by the study of a (5, 5) nanotube with pentagon-pentagon fusion ring. The high chemical reactivity of the topological defects of the BS-nanotubes is correlated to the presence of localized resonant states.