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Title: First-principles study of multiple order-disorder transitions in Cd{sub 2}AgAu Heusler alloys

Abstract

The bcc-based Heusler alloys exhibit a series of order-disorder phase transitions as a function of temperature. The high-temperature phase is a disordered bcc solid solution, and the low-temperature phase is the Heusler structure. An intermediate ordered phase is also typically observed in real systems. A prototype cluster variation method (CVM) analysis is presented that shows that the relative stabilities of the Heusler and intermediate phases can vary continuously, depending on a fine balance between ordering tendencies in the constituent binary systems. Given these basic conclusions, a first-principles analysis of order-disorder transitions in Cd{sub 2}AgAu was performed. A cluster expansion Hamiltonian was constructed based on a series of linearized muffin-tin orbital calculations in the atomic sphere approximation. CVM calculations were then performed in the ternary bcc tetrahedron approximation. In addition to the transition temperatures, long-range order parameters, and sublattice occupations for Cd{sub 2}AgAu, an isoplethal section of the ternary phase diagram was also calculated. In general, agreement with experiment is excellent, given the first-principles nature of the calculation. This study clearly demonstrates the ability of first-principles statistical-mechanical calculations to treat complex ordering phenomena in {ital ternary} systems. {copyright} {ital 1996 The American Physical Society.}

Authors:
;  [1]
  1. Department of Materials Science, University of California, Berkeley, California 94720 (United States)|[Lawrence Berkeley Laboratory, Materials Science Division, Berkeley, California 94720 (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory
OSTI Identifier:
390386
DOE Contract Number:  
AC03-76SF00098; AC36-83CH10093
Resource Type:
Journal Article
Journal Name:
Physical Review, B: Condensed Matter
Additional Journal Information:
Journal Volume: 54; Journal Issue: 14; Other Information: PBD: Oct 1996
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; HEUSLER ALLOYS; ORDER-DISORDER TRANSFORMATIONS; CADMIUM ALLOYS; GOLD ALLOYS; SILVER ALLOYS; TERNARY ALLOY SYSTEMS; SOLID SOLUTIONS; TEMPERATURE DEPENDENCE; MUFFIN-TIN POTENTIAL

Citation Formats

McCormack, R., and de Fontaine, D. First-principles study of multiple order-disorder transitions in Cd{sub 2}AgAu Heusler alloys. United States: N. p., 1996. Web. doi:10.1103/PhysRevB.54.9746.
McCormack, R., & de Fontaine, D. First-principles study of multiple order-disorder transitions in Cd{sub 2}AgAu Heusler alloys. United States. doi:10.1103/PhysRevB.54.9746.
McCormack, R., and de Fontaine, D. Tue . "First-principles study of multiple order-disorder transitions in Cd{sub 2}AgAu Heusler alloys". United States. doi:10.1103/PhysRevB.54.9746.
@article{osti_390386,
title = {First-principles study of multiple order-disorder transitions in Cd{sub 2}AgAu Heusler alloys},
author = {McCormack, R. and de Fontaine, D.},
abstractNote = {The bcc-based Heusler alloys exhibit a series of order-disorder phase transitions as a function of temperature. The high-temperature phase is a disordered bcc solid solution, and the low-temperature phase is the Heusler structure. An intermediate ordered phase is also typically observed in real systems. A prototype cluster variation method (CVM) analysis is presented that shows that the relative stabilities of the Heusler and intermediate phases can vary continuously, depending on a fine balance between ordering tendencies in the constituent binary systems. Given these basic conclusions, a first-principles analysis of order-disorder transitions in Cd{sub 2}AgAu was performed. A cluster expansion Hamiltonian was constructed based on a series of linearized muffin-tin orbital calculations in the atomic sphere approximation. CVM calculations were then performed in the ternary bcc tetrahedron approximation. In addition to the transition temperatures, long-range order parameters, and sublattice occupations for Cd{sub 2}AgAu, an isoplethal section of the ternary phase diagram was also calculated. In general, agreement with experiment is excellent, given the first-principles nature of the calculation. This study clearly demonstrates the ability of first-principles statistical-mechanical calculations to treat complex ordering phenomena in {ital ternary} systems. {copyright} {ital 1996 The American Physical Society.}},
doi = {10.1103/PhysRevB.54.9746},
journal = {Physical Review, B: Condensed Matter},
number = 14,
volume = 54,
place = {United States},
year = {1996},
month = {10}
}