knee-shaped junctions of semiconductor zig-zag carbon nanotubes were investigated. Two dissimilar octagons appear at such junctions; one of them could reconstruct into a pair of pentagons. The junction with two octagons presents two degenerate localized states at the Fermi energy. The reconstructed junction had only one state near the Fermi energy, indicating that these localized states were related to the octagonal defects. The inclusion of Coulomb interaction splits the localized states in the junction with two octagons, yielding an antiferromagnetic system.

Octagonal Defects at Carbon Nanotube Junctions. W.Jaskólski, M.Pelc