Density functional theory study on structural and mechanical properties of graphene, T-graphene, and R-graphyne

In the present work, structural and mechanical properties of T-graphene and R-graphyne were studied and compared with that of graphene. Cohesive energy, in-plane stiffness, Poisson's ratio, and in-plane bulk modulus were calculated based on density functional theory. It was found that absolute values of cohesive energy, in-plane stiffness, and bulk modulus of T-graphene are higher than that of R-graphyne, while T-graphene presents lower Poisson's ratio than R-graphyne. These results indicated that T-graphene possess higher stability and stiffness than R-graphyne. The less stability and easily deformable structure of R-graphyne is due to the porous structure and lower planar packing density of R-graphyne compared to T-graphene. The results also showed that both T-graphene and R-graphyne are softer than graphene. The maximum values of supported uniaxial and biaxial strains before failure were also determined. The results revealed that T-graphene and R-graphyne can be the proper candidates for applications in nanomechanics, especially when need softer materials than graphene.