Mechanical properties and instabilities of ordered graphene oxide C6O monolayers

We investigate the mechanical properties and instabilities of ordered honeycomb monolayer structures of graphene oxide C6O under various large strains using density functional theory. We found that the in-plane Young's modulus and intrinsic strengths are reduced by the oxidation of graphene with only the epoxy groups in ordered graphene oxide C6O by a factor of 20% and 33%, respectively, opposite to 11% increase of the Poisson's ratio. We obtained the second, third, fourth, and fifth order elastic constants for a rigorous continuum description of the nonlinear elastic response. The pressure effect on the second order elastic constants and Poisson's ratio were predicted from the third order elastic constants.