Instability of supersonic crack in graphene

The velocity and instability of crack motion in 2D hexagonal lattice of graphene under pure opening loads are investigated by atomistic molecular dynamics simulations. The brittle crack along zigzag direction in a strip can propagate supersonically at even 8.82 km/s under uniform normal loading of edge displacements. Crack moving straightly at low speeds produces atomically smooth edges, while kinking occur beyond a critical speed around 8.20 km/s equivalent to 65% of Rayleigh-wave speed in graphene, which validates previous theoretical predictions of rapid fracture instability in elastodynamics, and rough and irregular edges with oscillatory overhangs are formed subsequently.