A DFT study of chemical ordering and oxygen adsorption in AuPtPd ternary nanoalloys

The chemical ordering of AuPtPd trimetallic clusters is investigated by DFT calculations. Clusters of sizes 55 and 38 with icosahedral, decahedral and truncated octahedral structures are considered. A systematic search is performed for the Au-rich compositions Au42Pt13−nPdn (n = 0 −13) and Au32Pt6−nPdn (n = 0 −6), and for the Pd-rich Au12Pt13Pd30. The isomers relaxed at the DFT level are extracted by a structure database constructed by global optimization searches by an atomistic force field. The DFT calculations show that either (PtPd)@Au or Pt@(AuPd) core–shell chemical orderings are favourable for Au-rich and Pd-rich compositions, respectively. Au atoms tend to occupy lowest-coordination sites, while Pt atoms prefer the central core sites. The adsorption of atomic oxygen on the surface of the AuPtPd cluster is studied, determining the most favourable adsorption sites and the effect of sub-surface atoms and of surface impurities on adsorption energies.