Mechanical properties of the hexagonal boron nitride monolayer: Ab initio study

Using density functional theory (DFT) calculations we found that hexagonal boron nitride monolayer (h-BN) shows a non-linear elastic deformation up to an ultimate strength followed by a strain softening to the failure. To develop a continuum based model for such non-linear behavior, we proposed a method to study high order elastic constants of the 2D hexagonal structures. The continuum description of the elastic properties of monolayer h-BN is obtained using this method through ab initio density functional theory. This rigorous continuum description of the elastic response is formulated by expanding the elastic strain energy density in a Taylor series in strain truncated after the fifth-order term. we obtained a total of fourteen non-zero independent elastic constants for up to tenth-order tensor.