▎ 摘　　要

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.