Electronic properties of carbon nanotubes with pentagon-heptagon pair defects

Introduction of a pentagon-heptagon pair defect in the perfect hexagonal ne twork of two carbon nanotubes can change the helicity of the tube and alter its electronic structure. Using a tight binding method to calculate the el ectronic structure of such a system, we show that this pentagon-heptagon pa ir defect in the nanotube structure is not only responsible for the change in nanotube diameter, but also governs the electronic behavior around the F ermi level. This configuration is explored in order to understand the influ ence of the defect on the electronic properties of the system. Topological aspects associated with the presence of the defect are also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.