A computational NMR study on zigzag aluminum nitride nanotubes

A computational nuclear magnetic resonance (NMR) study is performed to investigate the electronic structure properties of the single-walled zigzag aluminum nitride nanotubes (AlNNTs). The chemical-shielding (CS) tensors are calculated at the sites of Al-27 and N-15 nuclei in three structural forms of AlNNT including H-saturated, Al-terminated, and N-terminated ones. The structural forms are firstly optimized and then the calculated CS tensors in the optimized structures are converted to chemical-shielding isotropic (CSI) and chemical-shielding anisotropic (CSA) parameters. The calculated parameters reveal that various Al-27 and N-15 nuclei are divided into some layers with equivalent electrostatic properties; furthermore, Al and N can act as Lewis base and acid, respectively. In the Al-terminated and N-terminated forms of AlNNT, in which one mouth of the nanotube is terminated by aluminum and nitrogen nuclei, respectively, just the CS tensors of the nearest nuclei to the mouth of the nanotube are significantly changed due to removal of saturating hydrogen atoms. Density functional theory (DFT) calculations are performed using GAUSSIAN 98 package of program.