Abstract: Using the extended Su-Schriffer-Heeger model,in the real space it investigates the features of energetics, the electronic properties of carbon nanotubes,containing pentagon-heptagon pairs(5/7),pentagon-hexagonal-heptagon (5/6/7) and pentagon-hexagonal-hexagonal-heptagon(5/6/6/7) topological defects in the perfect hexagonal network of the zigzag configuration.The present calculations show that the pentagon-heptagon pair defects on the nanotube structure are not only responsible for a change in nanotube diameter,but also govern the electronic behavior around Fermi level.By calculating the densities of states of the (9,0)-(8,0),(9,0)-(7,0) and (9,0)-(6,0) system,and the densities and band of these heterojuctions have been compared.These results show that the different arranges of pentagon and heptagon along the axi have obvious difference on electrical properties of carbon Nanotube.So different electronic devices based on these heterojuctions can be created.

Key words: carbon nanotube, molecular juction, heterojuction, topological defect, densities of states of the electronic