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

Vijay Gopal Chilkuri,Stefano Evangelisti,Thierry Leininger,Antonio Monari

doi:10.1155/2015/475890

Abstract

This paper presents atight bindingandab initiostudy 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 thetight bindingapproach show the existence of quasi-degenerate orbitals located around the Fermi level, thus suggesting the importance of high-qualityab initiomethods, 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.

Highlights

Besides the two lightest elements, hydrogen and helium, carbon is one of the most widespread elements in the universe and one of the best known ones
The computational details concerning both the ab initio and the tight binding approaches will be discussed in detail in order to facilitate the reproduction of our results
In order to explore the effect of a more realistic basis set, a limited number of structures representative of each class of nanotubes have been studied with a larger basis set, the cc-pVDZ correlation consistent basis set of Dunning [37]

Summary

Introduction

Besides the two lightest elements, hydrogen and helium, carbon is one of the most widespread elements in the universe and one of the best known ones. Its three-dimension allotropic forms, diamond and graphite, are well known since the antiquity. For this reason, the recent discovery of new low-dimensional allotropic forms, such as fullerenes, carbon nanotubes, and graphene, came out rather unexpected [1, 2]. A completely new branch of science was born, whose scientific and technological impact can hardly be overestimated. These findings had, and still have, an enormous importance in the discovery of novel and advanced materials and have been one of the key factors in the development of nanoscience. It is clear that a better understanding of these systems would make our knowledge of the general properties of solid-state physics and chemistry much deeper

Methods

Results

Conclusion