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First-Principles Study of Phase Stability in Pd-Rh Alloys

Published online by Cambridge University Press:  28 February 2011

D.D. Johnson
Affiliation:
Sandia National Laboratories, Livermore, CA 94550
P.E.A. Turchi
Affiliation:
Lawrence Livermore National Laboratory, Livermore, CA 94551
Marcel Sluiter
Affiliation:
Lawrence Livermore National Laboratory, Livermore, CA 94551
D.M. Nicholson
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN 37831
F.J. Pinski
Affiliation:
University of Cincinnati, Cincinnati, OH 45221
G.M. Stocks
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN 37831
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Abstract

We present a study of the mixing energies and the effective cluster interactions which form the configurational part of the internal energy of Pd-Rh substitutional alloys. We discuss the tendency towards phase-separation and more generally phase stability. The effects of a substitutional ternary addition on the tendencies toward order or phase-separation are also reported. The Korringa-Kohn-Rostoker Coherent-Potential Approximation (KKR-CPA) is used to investigate the electronic structure effects and energetics of the random alloy. Moreover, we use the Generalized Perturbation Method (GPM), using the KKR-CPA random alloy as a reference medium, to investigate the effective interactions which determine phase stability. We briefly comment on other factors which may give important contributions to the total free-energy of the alloy. We also contrast the GPM with the Connolly-Williams approach for calculating phase diagrams from first-principles. Finally, we explore the inadequacies of the frozen-potential and Harris approximations to the energetics of alloying.

Type
Research Article
Copyright
Copyright © Materials Research Society 1991

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