Ab Initio Investigation about the Possibility of Ferromagnetism Induced by Boron Vacancy in BN Nanotubes

We study structural deformation, electronic states, and intrinsic magnetism induced by the cation vacancy (VB) in boron nitride nanotubes (BNNTs), in comparison with the BN sheet, using spin-polarized density functional theory. Two types of vacancy configurations are observed in tubes, depending on the nature of the vacancy and the local stress. The underlying formation mechanisms are discussed from the viewpoint of the electronic and geometrical (or stress-induced) effects. Under additional stress, the VB prefers the open configuration to the closed 5-1DB configuration, showing different properties and potential applications. Due to the strong localization, the magnetic interaction between the VB-induced moments is short-range along either the axis or the circumference, meaning the ferromagnetism is difficult to be present. The simulation of negative charge injection implies VB-defective BNNTs might be promising candidates for spin-transport devices. In addition, the effects of surrounding H and F atoms on the spin-polarized states and magnetism of defective BNNTs are also explore