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 a single edge as well as at both edges. The number of lines (n) of the pentagon heptagon defect has been varied from 1 to 8 for 10-zBNNRs. Among the different spin-configurations that we have studied, we find that the spin-configuration with ferromagnetic ordering at each edge and antiferromagnetic 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 semiconductors, but, for even-numbered, all the systems show interesting antiferromagnetic 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 similar to 1.1 nm (6-zBNNR) to similar 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.