Phonon anomalies in. beta. -phase Ni sub x Al sub 1 minus x alloys
- Ames Laboratory, and Department of Physics, Iowa State University, Ames, Iowa 50011-3010 (United States)
The electronic band structure of {beta}-phase Ni{sub {ital x}}Al{sub 1{minus}{ital x}} has been calculated using a first-principles linear combination of atomic orbitals method, and then fitted by the nonorthogonal empirical tight-binding method for the evaluation of electron-phonon matrix elements. A Kohn-like anomaly in the TA{sub 2} branch along the (110) direction is attributed to both strong electron-phonon interactions and Fermi-surface nesting. Other phonon anomalies near {bold q}=0.55(1,1,1){pi}/{ital a} and {bold q}=0.6(1,0,0){pi}/{ital a} in {beta}-phase Ni{sub 0.50}Al{sub 0.50} are predicted. For the Ni{sub 0.625}Al{sub 0.375} composition, the TA{sub 2} anomaly shifts to smaller wave vectors and the phonon is predicted to be soft at {ital T}=0 K. Introducing a thermal smearing of the Fermi surface is enough to stabilize this mode, which occurs near (1/3, 1/3,0){pi}/{ital a} and is associated with the well-known martensitic transformation.
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 5007079
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 45:6; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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