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B2 Phases and their Defect Structures: Part I.I. Ab initio Vibrational and Electronic Free Energy in the Al-Ni-Pt-Ru System

Published online by Cambridge University Press:  26 February 2011

Raymundo Arroyave ,
Sara Prins  and
Zi-Kui Liu
Raymundo Arroyave
Affiliation:
Dept. Mat. Sci. & Eng., Pennsylvania State University, University Park, PA 16802, USA
Sara Prins
Affiliation:
Dept. Mat. Sci. & Eng., Pennsylvania State University, University Park, PA 16802, USA CSIR-NML, P.O. Box 395, Pretoria, 0001, South Africa
Zi-Kui Liu
Affiliation:
Dept. Mat. Sci. & Eng., Pennsylvania State University, University Park, PA 16802, USA
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Abstract

In this work, we calculate the finite temperature thermodynamic properties of the binary B2 phases in the Al-Ni-Pt-Ru system, particularly the B2 RuAl phase in the Pt-Al-Ru ternary, through the incorporation of the vibrational and electronic contributions to the total free energy. The harmonic approximation is used to consider the atomic vibrations, with the quasi-harmonic correction to account for volume expansion effects on the vibrational entropy as the temperature increases. The vibrational entropy calculations are incorporated through the supercell approach. The calculated phonon dispersion curves show that the B2 PtRu structure is mechanically unstable at low temperatures, while B2 PtAl is marginally stable. The thermal electronic contribution is added to the total free energy. Finally, the formation enthalpies and entropies of B2 RuAl are calculated as a function of temperature.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 842: Symposium S – Integrative and Interdisciplinary Aspects of Intermetallics , 2004 , S5.13
Copyright
Copyright © Materials Research Society 2005

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References

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