The properties of the electronic structure of the Disiline-doped boron nitride nanotubes (Disiline-BNNTs) are investigated by a density functional theory (DFT) calculation. The structural forms are firstly optimized and the CS tensors calculated. Subsequently, the chemical-shielding isotropic (CS I ) and chemical shielding anisotropic (CS A ) parameters are found. The shielding values of boron (B) and nitrogen (N) atoms were calculated by Gauge-Including Atomic Orbital (GIAO), Continuous Set of Gauge Transformations (CSGT) and Individual Gauges for Atoms in Molecules (IGAIM) methods, using B3LYP/6-311+G*. The B3LYP level of theory with IGAIM was the best method to evaluate the theoretical chemical shifts for studied models. The results reveal a significant effect of Disiline doping on the chemical shielding tensors at the sites of those 11 B and 15 N nuclei located in the nearest neighborhood of the Disiline-doped ring. Furthermore, the values of dipole moments and HOMO-LUMO gaps change in the Disiline-doped models in comparison with the original pristine model.Carbon and non-carbon nanotubes have come into special focus of researches and received increasing attention during the past 10 years, due to their unique and fascinating properties and wide potential applications [1-3]. The electronic and structural properties of BNNTs have been investigated by either computational [4,5] or experimental [6,7] studies.BNNTs are a structural analogy to CNTs that instead alternate boron and nitride atoms to replace the carbon atoms in the hexagonal structure.Although CNTs and BNNTs have similar structures, their properties are quite different. For example, the electronic properties of CNTs are distinctly different from those of BNNTs because of the large ionicity of B-N bonds [8]. Also, BNNTs have a much better resistance to oxidation in high temperature systems than CNTs [9]. In contrast with CNTs, which exhibit metallic or semiconducting behavior depending on the tubular diameter and chirality, BNNTs are viewed as always semiconductors without any dependence on the structural factors [10].Moreover, the BNNTs are polar materials because of slight positive charges of boron (B) atoms and the trivial negative charges of nitrogen (N) atoms whereas CNTs are non-polar.

Density functional theory (DFT) calculations have been performed to investigate the properties of the electronic structures of pyrazine-doped boron nitride nanotubes (PD-BNNTs). e structural forms were �rstly optimized and then nuclear magnetic resonance (NMR) parameters have been calculated on the optimized structures. e chemical shielding isotropic (CS I) and chemical shielding anisotropic (CS A) parameters were calculated at the sites of 11 B and 15 N nuclei in structural forms of BNNT including the perfect (a) model and PD-BNNTs (b), (c), and (d) models. e results indicated that the changes are most signi�cant for those nuclei placed in the nearest neighborhood of the pyrazine-doped ring. e changes of the electronic sites of the N atoms are also more signi�cant than those of the B atoms. e di�erence 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.

A computational study on the basis of density functional theory (DFT) calculations has been performed to investigate the properties of the electronic structure of (6,0) zigzag boron nitride nanotubes and two models ((a) and (b)) of diborinin-doped boron nitride nanotubes (DBD-BNNTs). e calculated structural energies yield similar values for two models of DBD-BNNTs. Isotropic (CS ) and anisotropic (CS ) chemical shielding parameters of the optimized BNNT and DBD-BNNTs are calculated. e results illustrate that the changes in chemical shielding tensors of 11 B and 15 N nuclei are more signi�cant in the nearest neighborhood of the diborinin ring due to doping process. e changes of the electronic sites of the N atoms are also more signi�cant than those of the B atoms. e dipole moments of the diborinin-doped BNNT structures show changes with respect to the pristine model. It is clear that the doping of diborinin ring decreases the energy gaps of the pure BNNT. For the pure model, the HOMO is located on the nitrogen atoms, and the LUMO is uniformly distributed throughout the B-N bonds. In contrast, for the diborinin-doped models, the majority of the HOMO and LUMO are located at the diborinin-doped regions.