Influence of Pyrazine Ring Doping on the 15N and 11B NMR and Electronic Structure Parameters in Zigzag Boron Nitride Nanotube : A DFT Study

Density functional theory (DFT) calculations have been performed to investigate the properties of the electronic structures of pyrazine-doped boron nitride nanotubes (PD-BNNTs). The structural forms were firstly optimized and then nuclear magnetic resonance (NMR) parameters have been calculated on the optimized structures. The chemical shielding isotropic (CSI) and chemical shielding anisotropic (CSA) parameters were calculated at the sites of 11B and 15N nuclei in structural forms of BNNT including the perfect (a) model and PD-BNNTs (b), (c), and (d) models. The results indicated that the changes are most significant for those nuclei placed in the nearest neighborhood of the pyrazine-doped ring. The changes of the electronic sites of the N atoms are also more significant than those of the B atoms. The difference of LUMO-HOMO gap for the perfect model was larger than the PD-BNNTs models. Also the atomic charge distribution of N and B atoms has been determined in nanotubes by natural bond orbital (NBO) analysis. All calculations were performed by the B3LYP method and 6-311G** basis set using Gaussian 98 package of program.