Effect of the dangling bond on the electronic and magnetic properties of BN nanoribbon

The effect of the dangling bond on the electronic and magnetic properties of BN nanoribbon with zigzag edge (ZBNNR) and armchair edge (ABNNR) have been studied using the first-principles projector-augmented wave (PAW) potential within the density function theory (DFT) framework. Though ZBNNR or ABNNR with H atom terminated at both edges is nonmagnetic semiconductor, the dangling bond induces magnetism for the ZBNNR with bare N edge, bare B edge, bare N and B edges, the ABNNR with bare N edge and bare B edge. However, the ABNNR with bare N and B edges is still nonmagnetic semiconductor due to the strong coupling of the dangling bonds of dimeric N and B atoms at the same edge. The magnetic moment of ZBNNR with bare N(B) edge is nearly half the magnetic moment of ABNNR with bare N(B) edge. Such a half relationship is also existed in the number of the dangling bond states appeared around the Fermi level in the band structures. Furthermore, the dangling bond states also cause both ZBNNR and ABNNR with bare N edge a transition from semiconducting to half-metallic and thus a completely (100%) spin-polarization, while cause both ZBNNR and ABNNR with bare B edge as well as ABNNR with bare N and B edges only a decrease in their band gap.