Magnetism and piezoelectricity of hexagonal boron nitride with triangular vacancy

First-principle calculations reveal that the configuration system of hexagonal boron nitride（h-BN） monolayer with triangular vacancy can induce obvious magnetism, contrary to that of the nonmagnetic pristine boron nitride monolayer.Interestingly, the h-BN with boron atom vacancy（VB-BN） displays metallic behavior with a total magnetic moment being 0.46μ;per cell, while the h-BN with nitrogen atom vacancy（VN-BN） presents a half-metallic characteristic with a total magnetic moment being 1.0μ;per cell. Remarkably, piezoelectric stress coefficient e;of the VN-BN is about 1.5 times larger than that of pristine h-BN. Furthermore, piezoelectric strain coefficient d;（12.42 pm/V） of the VN-BN is 20 times larger than that of pristine h-BN and also one order of magnitude larger than the value for the h-MoS;monolayer, which is mainly due to the spin-down electronic state in the V;-BN system. Our study demonstrates that the nitrogen atom vacancies can be an efficient route to tailoring the magnetic and piezoelectric properties of h-BN monolayer, which have promising performances for potential applications in nano-electromechanical systems（NEMS） and nanoscale electronics devices.