Ab Initio Study of Electronic Properties of a Armchair (7,7) Carbon Nanotube

Abstract

Ab initio Car-Parinnello molecular dynamics is used to simulate thestructure and the dynamics of 1-butyl-3-methylimidazolium iodide({[}bmim]I) ionic liquid at 300 K. Site-site pair correlation functionsreveal that the anion has a strong interaction with any three C-H's ofthe imidazolium ring. The ring bends over and wraps around the anionsuch that the two nitrogen atoms take a distance to the anion. Electrondonating butyl group contributes the electronic polarization inaddition to geometrical (out-of-plane) polarization of the ring due tothe liquid environment. This facilitates bending of the ring along theaxis passing through nitrogen atoms. The average bending angle dependslargely on the alkyl chain length and slightly on the anion type.Redistribution of electron density over the ring caused by the electrondonating alkyl group provides additional independent evidence to theinstability of lattice structure, hence the low melting point of theionic liquid. Simulated viscosity and diffusion coefficients of{[}bmim]I are in quite agreement with the experiments. (c) 2007American Institute of Physics.