Structural and electronic properties of TM23 - pAgp (TM = Ni, Pd, and Pt) clusters in the dilute limit (p = 0–4): A density functional theory investigation

We studied the structural, energetic, and electronic properties of free-standing binary clusters in the dilute limit, TM 23 − p Ag p with TM = Ni, Pd, and Pt, and p = 0–4, employing density functional theory within the generalized gradient approximation to the exchange-correlation energy functional, as implemented in the SIESTA code. For all studied systems, we found that the addition of Ag impurities decreases the binding energy of the clusters. The Ag impurities always prefer the surface sites, although not always the lowest coordination sites are occupied as it is observed in Pt, where large coordination surface sites are in general preferred. Clear Ag segregation is observed in Ni with the poly-icosahedral structure and Pt in the cubic-pyramidal structure. For Pd case a weak segregation and mixing patterns coexist depending upon which structure is shown, in the other cases in general a tendency to mixing is presented.