Short-range order for CuAu binary alloy: pseudopotential theory of the alloy revisited

• Published in: Journal of physics. F, Metal physics Metal physics, 1988-01, Vol.18 (1), p.21-32
• Main Authors: Khwaja, F A, Saif-ud-Din
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Materials science; Metals, semimetals and alloys; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Specific materials; Structure of solids and liquids; crystallography
• ISSN: 0305-4608
• DOI: 10.1088/0305-4608/18/1/005

An analysis of the electronic theory of short-range order based on the pseudopotential approximation has been carried out for the Cu--Au system. It is noticed that the theory in its simple form (i.e. based on a perfectly periodic lattice approximation) failed to predict the observed negative value of the order parameter for these alloys. The theoretical framework is re-examined in the light of static lattice distortions due to the difference in the sizes of the atoms for a solid solution of arbitrary concentration. The values of the ordering potential and order parameter are computed for Cu--50 at.% Au using different forms of the noble-metal model pseudopotentials. A comparison is made with experiments. It is concluded that the improved theoretical procedure yields at least qualitatively the observed negative values of the order parameter for this system. 25 ref.--AA