Theoretical and molecular dynamics studies on the negative Poisson's ratio of graphene regulated by epoxy groups

The negative Poisson's ratio (NPR) of graphene is studied via molecular dynamics (MD) simulations when epoxy groups are orderly arranged on its surface. When two epoxy groups are located on the same side of the zigzag bridge in a representative cell of graphene, a ripple area appears on the graphene surface. A truss structure model of the ripple is presented to reveal the nature of the NPR phenomenon due to the de-wrinkling effect during stretching. Based on this, the wrinkle region is defined as a periodic distribution unit, and it is evenly distributed along the X- and Y-direction in the 5 nm × 5 nm graphene, then it is found that graphene exhibits a remarkable negative Poisson's ratio phenomenon. In addition, the results show that the oxygen atoms proportion of graphene significantly influence its NPR, and the NPR is the most remarkable when the proportion of oxygen atoms is 4.2 %. [Display omitted] •NPR of graphene caused by epoxy group was studied by theoretical and MD method.•A truss structure model was presented to reveal the nature of NPR phenomenon.•The designed graphene containing epoxy groups exhibits remarkable NPR phenomenon.•NPR of graphene containing epoxy groups depends on the proportion of oxygen atoms.•GO with 4.2 % oxygen atoms has the most remarkable NPR.