2005-2006 Colloquium Series

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NAU Physical Sciences (Bldg 19, Rm 321), Monday, 12 September 2005, 4:00 PM
(Refreshments at 3:45pm)

Ordering Tendancies in the Binary Alloys of Rh, Pd, Ir and Pt.

Gus Hart
NAU

Abstract

The elements Rh, Pd, Ir and Pt are important because of their high catalytic potential, especially in alloys, and much work has been conducted to assess the properties of their alloys, especially their surfaces. Nevertheless, these alloys have been grossly misunderstood for nearly half a century. Since the 1950's it was thought that all six possible binaries of Rh, Pd, Ir and Pt exhibit phase-separating behavior. Recent findings have shown, however, that in the RhPt and PdPt systems, in fact, have negative mixing enthalpies, and ground state structures have been predicted. On the heels of this discovery, the present work has discovered similar behavior in the RhIr system. In view of the new information, it is critical that a complete reworking of our thinking about these binaries be conducted. In this work we consolidate the known information, and our new results, about the binary allows of the Rh-Pd-Ir-Pt quartet with the aim of producing a coherent picture of the ordering vs. phase separation behavior in these systems.

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