Compositional short-range ordering in metallic alloys: Band-filling, charge-transfer, and size effects from a first-principles all-electron Landau-type theory

Journal Article · Fri Jul 15 00:00:00 EDT 1994 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.50.1450· OSTI ID:7037658

Staunton, J B ^[1]; Johnson, D D ^[2]; Pinski, F J ^[3]

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1. Department of Physics, University of Warwick, Coventry CV7 4AL (United Kingdom)
2. Computational Materials Science Department, Sandia National Laboratories, Livermore, California 94551-0969 (United States)
3. Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221-0011 (United States)

Using a mean-field statistical description, we derive a general formalism to investigate atomic short-range order in alloys based on a density-functional description of the finite-temperature, grand potential of the random alloy. This first-principles,'' Landau-type approach attempts to treat several contributions (electronic structure, Fermi surface, electrostatics, magnetism, etc.) to the electronic energy on an equal footing. An important ingredient for the statistical averaging is the replacement of the molecular mean fields (Weiss fields) with Onsager cavity fields, which forces the diagonal part of the fluctuation-dissipation theorem to be obeyed. To show its general applicability and usefulness, we apply the theory to three fcc alloy systems. In Cu[sub 0.75]Pd[sub 0.25], the incommensurate atomic short-range order is driven by a Fermi-surface effect, in agreement with earlier work. In contrast, Pd[sub 0.5]Rh[sub 0.5] exhibits clustering tendencies, with both band-filling and charge-rearrangement effects being important in setting the spinodal temperature at 1150 K, in good agreement with experiment. In the final examples of three nickel-rich NiCr alloys, previously ignored electrostatic effects are found to play a significant role in determining the atomic short-range order.

• OSTI ID: 7037658
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 50:3; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHROMIUM ALLOYS
ORDER-DISORDER TRANSFORMATIONS
COPPER BASE ALLOYS
NICKEL ALLOYS
PALLADIUM ALLOYS
RHODIUM ALLOYS
CRYSTAL STRUCTURE
ELECTRONIC STRUCTURE
ENERGY-LEVEL DENSITY
MAGNETIC PROPERTIES
ORDER PARAMETERS
ALLOYS
COPPER ALLOYS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
PLATINUM METAL ALLOYS
360104* - Metals & Alloys- Physical Properties