Comparison between cluster and slab model for Pt-group atom adsorption on gold and silver substrate

The understanding of atomic adsorption on a solid surface is essential to understand the fundamental issue of chemical interaction at the hetero-junctions, formed by two metals. With an aim to compare the adsorption behavior between finite size cluster and extended surface, M atom (M = Ni, Pd, Pt) interaction with Agn/Aun (n = 3, 6) clusters and periodic slab of Ag(111)/Au(111) surfaces is investigated theoretically. All calculations are performed using plane-wave pseudo-potential approach under the spin-polarized density functional theory including the spin–orbit coupling term. The results show that the interaction of M atom with small clusters is primarily governed by the relative strength of MAg/Au vs. AgAg/AuAu bonds. The stronger interaction follows rearrangement of the host cluster. For the periodic slab, M atom prefers to adsorb on the fcc site with small local distortion. Due to variation in the strength of interaction and amount of distortion, the cluster and periodic slab differs in absolute adsorption energy values. Further a comparative analysis of chemical bonding through electronic density of state (EDOS) and orbital decomposed charge distribution infers that interaction of Ni/Pd/Pt with gold substrate is stronger than silver substrate.