Structural, magnetic, and electronic properties of Nin and Fen nanostructures (n=1-4) adsorbed on zigzag graphene nanoribbons

Extensive ab initio density-functional calculations were performed to investigate the structural, magnetic, and electronic properties of systems comprising Ni-n and Fe-n nanostructures (n=1-4) adsorbed on hydrogen-passivated zigzag graphene nanoribbons (GNRs). Both Ni and Fe atoms were most strongly bound at GNR edge sites and neither altered whether the GNR was metallic or semiconducting. However, Ni-n nanostructures were more strongly bound than Fe-n nanostructures, and their atoms had much smaller spin magnetic moments; Ni-n/GNR systems, like the pristine GNR, always had lowest energy with antiparallel edge spins, whereas among Fe-n/GNR systems this was only found for one- or two-atom adstructures at subedge or near-subedge atop sites; and zigzag Ni-3 and Ni-4 chains placed at GNR hole sites retained close contact with the GNR upon relaxation, whereas the analogous Fe chains adopted geometries similar to those of free-standing Fe clusters, with one or more atoms lifted away from the GNR.