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Molecular Dynamics Study of Formation by Interdiffusion of Pd-Ni and Ag-Ni Nanoparticles |
| Alexander V. Evteev , Elena V. Levchenko , Irina V. Belova , Graeme E. Murch |
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The University of Newcastle, University Drive, Newcastle 2308, Australia |
| Abstract |
Nanoparticles are very promising materials for advanced magnetic, catalytic, optical, electronic, photonic, pharmaceutical and biomedical applications, due to their specific structure and unique physical and chemical properties at the nanoscale, which cannot be observed in bulk material. In principle, the properties of alloy nanoparticles can be tuned by varying the composition, size, shape and atomic ordering, but exactly how this can be achieved remains largely unknown. In the case of alloy nanoparticles, surface segregation plays the major role for the understanding of their structure and functional properties. In this work, we have carried out a series of long-time scale molecular dynamics simulations of Pd-Ni and Ag-Ni nanoparticles with different compositions and sizes using many-body potentials. We have demonstrated that a novel kind of structure of Pd-Ni alloy nanoparticles can be self-assembled by interdiffusion from an initial Ni (core)-Pd (shell) f.c.c structure. In this self-assembled structure, the Ni atoms mostly accumulate in a layer just below the surface. Meanwhile, the Pd atoms cover this Ni layer from inside and outside by two Pd layers. In sharp contrast to the Pd-Ni system, in the system Ag-Ni, Ag and Ni have almost complete insolubility. The initial state was the f.c.c. structure wherein a core of Ag atoms was surrounded by shell of Ni atoms. Then during isothermal annealing at various temperatures we observed a tree-shell Ag-Ni-Ag structure of the nanoparticles formed by segregation of Ag atoms to the surface. We established that Pd-Ni and Ag-Ni alloy nanoparticle structure is likely to depend strongly on alloy composition and nanoparticle size. Our results indicate a new possibility for controlling the chemical ordering in Pd-Ni and Ag-Ni system at the nanoscale level. Such segregated nanoparticles should have unique physical and chemical properties (applications). |
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Presentation: Oral at E-MRS Fall Meeting 2008, Symposium G, by Elena V. LevchenkoSee On-line Journal of E-MRS Fall Meeting 2008 Submitted: 2008-05-12 06:04 Revised: 2009-06-07 00:48 |