Phase stability and electronic structure of ScAl sub 3 and ZrAl sub 3 and of Sc-stabilized cubic ZrAl sub 3 precipitates
- Department of Physics and Astronomy, Northwestern University, Evanston, IL (USA) Shanghai Institute of Metallurgy, Academy of Sciences of China, Shanghai 200050 (China)
- Department of Physics and Astronomy, Northwestern University, Evanston, IL (USA)
The structural stability and the electronic structure of ScAl{sub 3} were studied using an all-electron, total-energy, local-density approach. The calculated results show that ScAl{sub 3} in the {ital L}1{sub 2} structure is energetically favored compared with the {ital D}0{sub 22} structure by about 0.42 eV per formula unit. The calculated lattice constant (4.055 A) is in fairly good agreement with experiment (4.10 A). As a comparison, the calculated electronic and cohesive properties for ZrAl{sub 3} in its metastable {ital L}1{sub 2} and {ital D}0{sub 22} phases are also presented. It is argued, on the basis of density-of-states results, that a cubic Zr{sub 1{minus}{ital x}}Sc{sub {ital x}}Al{sub 3} compound (and also Ti{sub 1{minus}{ital x}}Sc{sub {ital x}}Al{sub 3}) might be a good candidate as a dispersed phase in the aluminum alloys for elevated temperature applications. To test this prediction, we determined the electronic structure and the stability of Sc-stabilized cubic (Zr{sub 0.5}Sc{sub 0.5})Al{sub 3} using the same total-energy approach. The calculated total energy for (Zr{sub 0.5}Sc{sub 0.5})Al{sub 3}, which is about 0.24 eV per unit cell lower than the sum of the total energies of ZrAl{sub 3} and ScAl{sub 3}, clearly indicates that cubic (Zr{sub 0.5}Sc{sub 0.5})Al{sub 3} is energetically favored compared with a mixture of its constituents. Finally, an analysis of the results indicates that the stability of the aluminides appears to be understood in the rigid-band sense in terms of the band filling of the bonding states.
- OSTI ID:
- 7025583
- Journal Information:
- Physical Review, B: Condensed Matter; (USA), Vol. 41:18; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM ALLOYS
ELECTRONIC STRUCTURE
PHASE STABILITY
ALUMINIUM COMPOUNDS
SCANDIUM ALLOYS
ZIRCONIUM ALLOYS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
LATTICE PARAMETERS
TEMPERATURE DEPENDENCE
ALLOYS
STABILITY
360102* - Metals & Alloys- Structure & Phase Studies
360104 - Metals & Alloys- Physical Properties