Electronic and Magnetic Properties of Zigzag Boron-Nitride Nanoribbons with Even and Odd-line Stone-Wales (5-7 pair) Defects

Spin-polarized first-principles calculations have been performed on zigzag Boron-Nitride Nanoribbons (z-BNNRs) with lines of alternating fused pentagon (P) and heptagon (H) rings (Pentagon-Heptagon-line-defect) at single edge as well as at both edges. The number of line (n) of the Pentagon-Heptagon-defect has been varied from 1 to 8 for 10-zBNNRs. Among the different spin-configurations which we have studied, we find that, the spin-configuration with ferromagnetic ordering at each edge and anti-ferromagnetic ordering across the edges is quite interesting. For this spin-configuration, we find that, if the introduced PH-line-defect is odd numbered, the systems behave as spin-polarized semi-conductors, but, for even numbered, all the systems show interesting anti-ferromagnetic half-metallic behavior. Robustness of these results has been cross checked by the variation of the line-defect position and also by the variation of the width [from ~ 1.1 nm (6-zBNNR) to ~ 3.3 nm (16-zBNNR)] of the ribbon. Density of States (DOS), projected-DOS and band-structure analysis have been accomplished to understand the reasons for these differences between even and odd-line-defects. The main reason for many of the observed changes was traced back to the change in edge nature of the BNNR, which indeed dictates the properties of the systems.