Grain boundaries guided vibration wave propagation in polycrystalline graphene

Molecular dynamics (MD) simulations are performed to study the propagation of mechanical transverse wave in both single-crystal and polycrystalline graphene sheets. It is found that the vibration propagation in graphene sheet behaves in damping oscillation. The wave propagation in single-crystal graphene sheet is anisotropic as a result of orientation dependent phase velocity but is completely isotropic in polycrystalline ones. Particularly, the propagation velocity in grain boundaries (GBs) is much faster than that in grains, and the vibration amplitude at GBs is substantially larger than that in grains as a result of reduced bonding force and the lower mass density in GBs. The large out-of-plane displacement regions distribute along the GBs. It is believed that the GBs could be more capable of absorbing energy from the waves, but have less capability to spread the gained energy again.