Phonons in random alloys: The itinerant coherent-potential approximation

Subhradip Ghosh, P. L. Leath, Morrel H. Cohen

Research output: Contribution to journalArticle

47 Scopus citations

Abstract

We present the itinerant coherent-potential approximation (ICPA), an analytic, translationally invariant, and tractable form of augmented-space-based multiple-scattering theory18 in a single-site approximation for harmonic phonons in realistic random binary alloys with mass and force-constant disorder. We provide expressions for quantities needed for comparison with experimental structure factors such as partial and average spectral functions and derive the sum rules associated with them. Numerical results are presented for Ni55Pd45 and Ni50Pt50 alloys which serve as test cases, the former for weak force-constant disorder and the latter for strong. We present results on dispersion curves and disorder-induced widths. Direct comparisons with the single-site coherent potential approximation (CPA) and experiment are made which provide insight into the physics of force-constant changes in random alloys. The CPA accounts well for the weak force-constant disorder case but fails for strong force-constant disorder where the ICPA succeeds.

Original languageEnglish (US)
Article number214206
Pages (from-to)2142061-21420616
Number of pages19278556
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume66
Issue number21
StatePublished - Dec 1 2002
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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