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Advances in Condensed Matter Physics
Volume 2015, Article ID 475890, 14 pages
http://dx.doi.org/10.1155/2015/475890
Research Article

The Electronic Structure of Short Carbon Nanotubes: The Effects of Correlation

1Laboratoire de Chimie et Physique Quantiques, IRSAMC, Université de Toulouse et CNRS, 118 Route de Narbonne, 31062 Toulouse Cedex, France
2Université de Lorraine, Nancy, Théorie-Modélisation-Simulation, SRSMC, Boulevard des Aiguillettes, 31062 Vandœuvre-lès-Nancy, France
3CNRS, Théorie-Modélisation-Simulation, SRSMC, Boulevard des Aiguillettes, 31062 Vandœuvre-lès-Nancy, France

Received 20 April 2015; Revised 16 July 2015; Accepted 5 August 2015

Academic Editor: Ashok Chatterjee

Copyright © 2015 Vijay Gopal Chilkuri et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This paper presents a tight binding and ab initio study of finite zig-zag nanotubes of various diameters and lengths. The vertical energy spectra of such nanotubes are presented, as well as their spin multiplicities. The calculations performed using the tight binding approach show the existence of quasi-degenerate orbitals located around the Fermi level, thus suggesting the importance of high-quality ab initio methods, capable of a correct description of the nondynamical correlation. Such approaches (Complete Active Space SCF and Multireference Perturbation Theory calculations) were used in order to get accurate ground and nearest excited-state energies, along with the corresponding spin multiplicities.