  The deformation and disintegration of a graphene nanoribbon under external
electrostatic fields are investigated by first principle quantum mechanical
calculations to establish its stability range. The zigzag edges terminated by
various functional groups are considered. By analyzing the phonon spectrum, the
critical fracture field for each edge structure is obtained. It is found that
different terminal groups on the zigzag graphene nanoribbons lead to different
fracture patterns at different fracture fields. The failure mechanism is
demonstrated to rely on both the carbon bond alternation feature across the
ribbon and terminal group electronegativity.
