Adsorption Structures and Energies of Cun Clusters on the Fe(110) and Fe3C(001) Surfaces

Spin-polarized density functional theory computations have been carried out to investigate the adsorption configurations of Cu-n (n = 1-7, 13) on the most stable Fe(110) and Fe3C(001) surfaces. On both surfaces the adsorbed Cu-n clusters favor aggregation over dispersion, and monolayer adsorption configurations are more favored thermodynamically than the two-layer adsorbed structures because of the stronger Fe-Cu interaction over the Cu-Cu bonding. On the basis of the computed adsorption energies the Fe(110) surface has stronger Cu affinity than the Fe3C(001) surface, in agreement with the experimental results. The Fe(110) surface also has stronger Cu-n aggregation energies and more pronounced charge transfer from surface to adsorbed Cu-n clusters than the Fe3C(001) surface. Different Cu-n growth modes have been discussed accordingly.