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Lattice trapping is an important aspect in accurately understanding the fracture behaviors of nanomaterials. Employing molecular dynamics simulations, we studied the lattice trapping of nanocracks in both single-crystal and polycrystalline graphene. Different crack-dislocation and crack-grain boundary configurations were constructed and investigated. It is found that cracks in single-crystal graphene exhibit negligible lattice trapping, with or without the presence of dislocations. On the other hand, lattice trapping in polycrystalline graphene may vary greatly and is shown to be directly correlated to the tensile strength of grain boundary. Moreover, we showed that unique dislocation-independent traction-separation behaviors, which are not affected by the presence of dislocations, exist for cracks in single-crystal graphene. The traction-separation relation was then fitted to a cohesive zone model to demonstrate the possibility of bridging atomistic modeling with large-scale numerical simulations. Our findings provide critical hints for atomistic-informed multiscale modeling of fracture of two-dimensional materials. [ABSTRACT FROM AUTHOR]

Hydrogenation is a viable approach in transforming two-dimensional (2D) nanosheets into three-dimensional (3D) nanoarchitectures. The present work reported self-folding of 2D graphene into 3D graphene Miura origami assisted by hydrogenation, and studied its Poisson's ratio under external strain using molecular dynamics simulation and continuum modeling. It was found that the graphene Miura origami possesses negative Poisson's ratio, being largely insensitive to the chirality of the folding creases and side lengths of the constituting parallelograms. We further demonstrated the good agreement of Poisson's ratio between the continuum prediction and MD simulation, and identified the origin of their deviation as localized stress concentration at the quad-junction of the graphene Miura origami. The present study provides insights into designing novel 3D nanoarchitectures of programmable functionalities from 2D nanomaterials. • Self-folding of graphene into graphene Miura origami was achieved by selective hydrogenation. • Poisson's ratio behavior was systematically studied by molecular dynamics simulation and continuum modeling. • Effects of chirality of folding, side lengths of constituting parallelograms, and local deformation were clarified. [ABSTRACT FROM AUTHOR]