Mechanical stabilities and properties of graphene and its modification by BN predicted from first-principles calculations

We investigate the mechanical stabilities and properties of graphene under various strains using first-principles planewave calculations based on density functional theory. We report the mechanics dependence of the graphene-like boron nitride (g-BN) concentration, including the high-order elastic constants and mechanical failure. Acting anisotropically, a large nonlinear elastic deformation up to the ultimate strength of the material, followed by a strain softening is observed. The ultimate strains in heterogeneous configurations are smaller than those in pure graphene and g-BN, which is related to the heterogeneity of the g-BNC monolayer. The in-plane stiffness as well as third-order elastic constants of graphene can be linearly tuned with g-BN concentration. The fourth- and fifthorder elastic constants have a more complex response to BN modification. The longitudinal mode elastic constants are sensitive to the BN modification in contrast with the shear mode elastic constants. The third-, fourth-, and fifth-order elastic constants are required for accurate modeling of the mechanical properties of g-BNC under strains greater than 0.02, 0.06, and 0.12, respectively. This study may provide guidance in tuning the mechanical properties through chemical modification of graphene by BN to optimize the function of graphenebased nanodevices, as well as their safe ranges of strain for the demanded engineering.