DFT calculations of structures, 13C NMR chemical shifts and Raman RBM mode of simple models of ultra small diameter (4,0) zigzag hydroxylated single wall carbon nanotubes

Selected acenes, cyclic acenes and model zigzag (4,0) single wall carbon nanotubes (SWCNTs) with one hydroxylic group at the open end were fully optimized at the B3LYP/6-31G* level of theory. The impact of molecule size on the B3LYP/pcS-2 calculated C-13 NMR chemical shifts was studied to characterize pristine and tip-monofunctionalized ultra narrow SWCNTs. The harmonic frequency of Raman radial breathing mode (RBM) was determined for monohydroxylated cyclic acenes and correlated with their diameter. A regular convergence of selected CC bond lengths, RBM frequency and carbon chemical shifts upon increasing the size of the systems was observed and fitted toward very large systems with two-parameter mathematical formula. The observed values of selected structural, Raman and C-13 NMR chemical shifts in the studied models point out toward a feasibility of NMR technique as a tool for characterization of pristine and OH-functionalized SWCNT materials. (C) 2012 Elsevier B.V. All rights reserved.