On the basis of first principles calculations, we report energy estimated to
cut a graphene sheet into nanoribbons of armchair and zigzag configurations.
Our calculations show that the energy required to cut a graphene sheet into
zigzag configuration is higher than that of armchair configuration by an order
of 0.174 eV. Thus, a control over the threshold energy might be helpful in
designing an experiment for cutting a graphene sheet into smooth edged armchair
or zigzag configurations