The effect of grain boundaries on the mechanical properties and failure behavior of hexagonal boron nitride sheets

In this work, the effect of grain boundaries (GBs) on the mechanical properties and failure behavior of two-dimensional hexagonal boron nitride (h-BN) sheets are systematically and comprehensively investigated using density functional theory. Results show that the formation of homoelemental bonds on GBs is an important factor, which could affect the atomic structures and stability of the h-BN sheet. The relationship between the formation energy and the misorientation angles is downward opening parabolic. The intrinsic strength shows an obvious decreasing trend with increasing inflection angles, while it shows a periodic dependence on the increase in misorientation angles. Thus, the mechanical properties of h-BN are significantly influenced by GBs. The h-BN sheets with different types of GBs show varied failure behavior, which are caused by the distinct stress distribution on GBs. The information obtained in this study would be useful for the understanding of GBs on the h-BN surface.