A Theoretical Study of Novel Composite Clusters of Platinum Metals*

Material shell composites.of platinum (Pt) and palladium metals have great stability and remarkable physical and chemical properties. In light of our previous work on the small atomic clusters on metallic clusters, we present here an Ab-initio quantum-mechanical study of the Pt_n, Ir_n, and Os_n ( n= 1-9 ) clusters, their hybrids M_iN_j ( M= Pt, Ir, Os; N= Pt, Ir, Os; i= 1-6; j= 1-6), and their composites of these metal clusters with palladium (Pd) clusters. Our theoretical approach is to utilize the ab initio methods of quantum chemistry to derive optimal geometries for the clusters of interest. Of particular interest in this research are the Pt₆ and Pt₈ rectangular parallelepipeds, and the Pt₈, Pt_9, Pt₈Pd₈, Pt₈Pd₉ cubic clusters. We examine the implications of this research for the self-assembly of metallo-supramolecular structures, by the directional bonding approach. Also, of interest here is the recent experimental work that showed that Pt clusters deposited on Pd shell over Au core nanoparticles (Au@Pd@Pt NPs) exhibit unusually high electrocatalytic activity for the electro-oxidation.