Computational studies on boron nitride and boron phosphide nanotubes: Density functional calculations of boron-11 electric field gradient tensors

We have performed density functional theory (DFT) calculations employing BLYP exchange functional and 6–31 G* standard basis set by GAUSSIAN 98 package of program. The electronic structure properties of representative zigzag and armchair models of boron nitride nanotube (BNNT) and boron phosphide nanotube (BPNT) have been studied. The (6,0) and (4,4) structures have been optimized and the electric field gradient (EFG) tensors have been calculated at the sites of various boron-11 nuclei. The calculated EFG tensors have been converted to the equivalent experimental nuclear quadrupole resonance (NQR) parameters, quadrupole coupling constant and asymmetry parameter. The results revealed that the boron atoms at the edges of nanotubes play dominant roles in determining the electronic behaviors of BNNT and BPNT. The average of the calculated values of quadrupole coupling constants at the sites of boron-11 nuclei is in good agreement with experiments.