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XUYANG XIAO,DONGPING SHI,JIHONG XIA,ZHENGFU CHENG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.6
Atomic segregation in bimetallic clusters can influence the surface nucleation and also the structures of clusters. It is important to study the effect of atomic segregation on the structure. In this study, initial cooling temperatures were used to tune the atomic segregation ability. Molecular dynamics simulation with an embedded atom method was used to study the relationship between the structure and atomic segregation. It was found that the higher the initial cooling temperature, the more obvious the Ag atomic segregation. When the clusters cooled down from 800 K and 600 K, the clusters formed a mixed icosahedron due to the weak atomic segregation ability. When the initial cooling temperature is higher than 1200 K, all the Ag atoms segregated to the surface layer, the clusters formed a Pd–Ag-core–shell chemical ordering. For 1200 K initial temperature, the structure is decahedral. The clusters formed an fcc structure when the clusters cooled down from 2000 K, 1800 K, and 1500 K. When the clusters cooled down from 860 K and 900 K, not all the Ag atoms segregated to the surface layer, the clusters formed a core–shell chemical ordering with a mixed Pd–Ag core. But the structure of 860 K is twinned of icosahedron and decahedron and that of 900 K is decahedral. This means that the chemical orderings and structures were influenced by the atomic segregation.
Zhijian Fu,Li-Jun Jia,JIHONG XIA,Hai-Bo Ruan,Ke Tang,Yong Pu,Zhao-Yi Zeng,Dian-Yong Tang,Bo Kong,Qi-Feng Chen 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.6
The equilibrium structure and electronic properties of four ultrathin free-standing pentagonal and hexagonal noble metal nanowires, that is, copper nanowires (CuNWs), silver nanowires (AgNWs), gold nanowires (AuNWs) and platinum nanowires (PtNWs), have been studied comprehensively by adopting a first-principles simulation based on the density-functional theory. The staggered topologies are more stable than the eclipsed ones by analyzing the bonding energy. The staggered ones with a linear atom chain in the center of the pentagonal or hexagons topologies are the preferred structures for CuNWs and AgNWs, but the staggered ones without a linear atom chain in the center of the pentagon or hexagon are the preferred structures for AuNWs and PtNWs due to the increasing core–core repulsions. The calculated electronic band structures and density of states present that all the noble metal nanowires are metallic. The projected densities of states (PDOS) of dominant d-states and the charge density show that the narrower d-state moved to the Fermi energy and metallic bonding character for all the noble metal nanowires.