Structural and electronic properties of Aun?xPtx (n = 2–14; x ? n) clusters: The density functional theory investigation

摘要

The structural evolutions and electronic properties of bimetallic Au n–x Pt x (n = 2–14; x ? n) clusters are investigated by using the density functional theory (DFT) with the generalized gradient approximation (GGA). The monatomic doping Au n–1Pt clusters are emphasized and compared with the corresponding pristine Au n clusters. The results reveal that the planar configurations are favored for both Au n–1Pt and Au n clusters with size up to n = 13, and the former often employ the substitution patterns based on the structures of the latter. The most stable clusters are Au 6 and Au 6Pt, which adopt regular planar triangle (D 3h ) and hexagon-ring (D 6h ) structures and can be regarded as the preferential building units in designing large clusters. For Pt-rich bimetallic clusters, their structures can be obtained from the substitution of Pt atoms by Au atoms from the Pt n structures, where Pt atoms assemble together and occupy the center yet Au atoms prefer the apex positions showing a segregation effect. With respect to pristine Au clusters, Au n Pt clusters exhibit somewhat weaker and less pronounced odd-even oscillations in the highest occupied and lowest unoccupied molecular-orbital gaps (HOMO-LUMO gap), electron affinity (EA), and ionization potential (IP) due to the partially released electron pairing effect. The analyses of electronic structure indicate that Pt atoms in AuPt clusters would delocalize their one 6s and one 5d electrons to contribute the electronic shell closure. The sp-d hybridizations as well as the d-d interactions between the host Au and dopant Pt atoms result in the enhanced stabilities of AuPt clusters.