  In this paper, we have studied functionalization of 5-7 edge-reconstructed
graphene nanoribbons by ab initio density functional calculations. Our studies
show that hydrogenation at the reconstructed edges is favorable in contrast to
the case of unreconstructed 6-6 zigzag edges, in agreement with previous
theoretical results. Thermodynamical calculations reveal the relative stability
of single and dihydrogenated edges under different temperatures and chemical
potential of hydrogen gas. From phonon calculations, we find that the lowest
optical phonon modes are hardened due to 5-7 edge reconstruction compared to
the 6-6 unreconstructed hydrogenated edges. Finally, edge functionalization by
Fe atoms reveals a dimerized Fe chain structure along the edges. The magnetic
exchange coupling across the edges varies between ferromagnetic and
antiferromagnetic ones with the variation of the width of the nanoribbons.
