Effect of nanotube length on the aromaticity and CSI parameters of finite length single-wall zigzag and armchair boron nitride nanotubes

Density functional theory (DFT) is used to determine chemical-shielding isotropic (CSI) and nucleus-independent chemical shift (NICS), an index of local aromaticity, for the composing of finite length (6, 0) and (4, 4) single-wall boron nitride nanotubes (BNNTs) as a function of their length for the first time. One of the highlights of the study is different CSI values of middle layers for both zigzag and armchair BNNTs, whereas the values do not change much for the middle layers with increase of the nanotube lengths. So the computed CSI values may spread and apply to the longer nanotubes. The NICS variations beside zigzag BN nanotubes are more significant within armchair BNNTs with increase of nanotube length.