Influence of Mn-doping on the chemical shielding tensors of 71Ga and 15N in the armchair GaN nanotubes: A DFT study

The chemical shielding (CS) tensors of Gallium-71 and nitrogen-15 are computed for the first time in order to investigate the influence of Mn-doping on the electronic properties of the (5, 5) Gallium nitride nanotube (GaNNT). A GaNNT consisting of 40 Ga and 40 N atoms and having a 1.2 nm length was considered. One portal of the nanotube was capped by ten hydrogen atoms and other-end was kept open. Additionally, two other forms of this model of Mn-doped GaNNT were considered where a Mn-atom was substituted for a Ga atom either in the first or in the second layer. The calculations reveal that in both models of Mn-doped GaNNTs, the N atoms that are directly connected to the Mn atom have the smallest isotropic chemical shielding among other N atoms. These calculations were performed at the level of the density functional theory (DFT) using GAUSSIAN 03 package. The basis sets for Ga and N atoms were chosen to be 6-31G (d) and those for Mn atom were chosen to be LanL2DZ.