The distorted K₁ soft mode of hexagonal-BN sheet and effects of charge doping

We demonstrate the distorted K₁ soft mode for the phonon instability of single layer hexagonal-BN sheet under tension, which is different from the well known K₁ mode failure mechanism of graphene. We also investigate the influences of charge doping on the soft mode phonon instability. Meanwhile, the ideal strength is found to be larger for both p- and n-type doped h-BN sheet, reflecting the electronic strengthening effect as similar as graphene. Our results reveal a different soft mode for h-BN sheet from that of graphene and can serve as references for future applications of h-BN sheet.