▎ 摘　　要

The elastic and fracture properties of both two-dimensional graphene and three-dimensional graphite were calculated based on molecular mechanics method, including the atomic bonding (stretching and bending) and non-bonding (van der Waal) energies. Since graphene and graphite are periodically arranged atomic structures, the representative unit cell could be chosen to illustrate their deformations under uniform loadings. The carbon bond length and angle changes of the graphene/graphite as well as the interlayer distance variations of the graphite under various loading conditions could be realized numerically under the geometry constraints and minimum energy assumption. It was found that the mechanical properties of graphene/graphite demonstrated distinct directional dependences at small and large deformations. In elastic region, graphene was in-plane isotropic, while graphite was transversely isotropic with the symmetry axis along out-of-plane direction. Meanwhile, the in-plane deformation of the representative unit cell was not uniform along armchair direction due to the discrete and non-uniform distributions of the atoms. The fracture of graphene/graphite could be predicted based on critical bond length criteria. It was noticed that the fracture behavior were directional dependent, and the fracture strain under simple tension was lower while loading on zigzag edge of graphene/graphite, which was consistent with molecular dynamics simulation results.