Thank you for your prompt response.
To the best of my knowledge, time taken by a hydrogen atom to get bonded with carbon atoms when C-C bonds breaks is too high. And, such processes cannot be studied with MD time scales with out external pressure.
In my fracture studies with graphene, I have seen self healing of cracks generated by applying tensile stress. What I did exactly is, I have given tensile stress to graphene sheet and relaxed it just after the crack propagation. Surprisingly, all cracks formed are getting healed.
I just want to know such crack closing happen in real atomsphere containing hydrogen or not ?