An investigation of curvature effects on the nitrogen and boron chemical shielding tensors as well as NICS characterization of BN nanotubes with Stone–Wales defects: A DFT study

A DFT study has been performed to investigate electronic and magnetic properties of armchair (4, 4), (5, 5), and (6, 6) BNNTs with Stone–Wales defects based on 11B and 15N NMR parameters and NICS indices. The smallest 15N chemical shielding arising from B1–N1 bond appears as an individual peak at around 97.0–99.4 ppm for “Parallel” orientation of the defect site (P-SW) and at around 87.0–88.8 ppm for “Diagonal” orientation of the defect site (D-SW), respectively, quite well separated from the rest of the spectrum. These results indicate that 15N NMR patterns might be able to detect the presence of SW defects found in BNNTs. The smallest 11B chemical shielding appears around 68.6–69.3 (P-SW) or 71.6–72.1 ppm (D-SW) arising from the boron surrounded by three different rings. Moreover, CS tensors are shown to be quite sensitive to the curvature at the corresponding site. Finally, NICS at ring centers and along principal axis are calculated to evaluate electron motilities on the surfaces and inside BNNTs. NICS values inside BNNTs with Stone–Wales defect is similar to the parent where the compensation between diatropic and paratropic ring currents leads to the uniformity of magnetic field, but slightly increases only in the zone of defect site.

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► Defect site yields shifts at which are separated from the rest of the NMR signal.
► CS tensors are shown to be quite sensitive to the curvature at the corresponding site.
► NICS values along the principal axes are similar to the parent but only in the zone of defect sites slightly increased.