Dynamic bimetallic systems

Surface-to-subsurface migrations in bimetallic NPs can completely change the surface composition and drastically alter catalytic performance. Despite the importance of atomic mobility in bimetallic systems, little is known about the dynamic processes of NPs and clusters due, in large part, to the lack of suitable experimental techniques. 

Recent studies suggest that small NPs are far more fluid than initially thought. Lower melting points [9] and the dominance of surface energies [10] in small NPs suggest that these systems may be quite dynamic, which can be used to make new nanomaterials. By exploiting the differences in adsorbate bond enthalpies to different metals in small bimetallic NPs [8, 11], randomly mixed alloys can be... 

The recent accomplishments of near-edge X-ray absorption spectroscopy in catalysis studies are already quite impressive, in particular if one considers the limited availability of suitable X-ray spectrometers. Developments of catalytic interest have concerned the Shell Higher Olefin process, size effects, metal-support interaction, mono- and bimetallic catalysts (in particular the PtRe/Al203 system), the reactivity of supported metal catalysts, dynamical and in situ catalyst studies, and a variety of oxide and sulfide catalysts. Other catalytic problems are now coming within easy experimental reach, such as the study of sulfur poisoning and the nature of coking. 

In an interesting study, Sankaranarayanan et compared bimetallic nanowires with clusters and the macroscopic crystals. They performed molecular-dynamics simulations using the Sutton-Chen potential for an approximate description of the interatomic interactions. They considered two systems, Pd-Rh and Pd-Cu. As initial structures, they considered cut-outs of the infinite, crystalline fee or hep structures. Subsequently, the two types of atoms were distributed at those atomic positions that led to the... 

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