Medium-ranged interactions of transition-metal (3d and 4d) impurity pairs in Al and atomic structures of Al-rich Al–transition-metal alloys

• Published in: Journal of alloys and compounds Vol. 434; pp. 572 - 576
• Main Authors: Hoshino, T., Fujima, N., Asato, M., Tamura, R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2007
• Subjects: Full-potential KKR; Generalized-gradient approximation in density-functional theory; Many-body interaction; Medium-ranged X–X interaction; sp-d Hybridization; sp-d Hybridization; Full-potential KKR; Generalized-gradient approximation in density-functional theory; Many-body interaction; Medium-ranged X–X interaction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2006.08.191

We give systematic ab initio calculations for the interaction energies (from first to eighth neighbors) of impurity pairs X–X (X = Sc–Zn, Y–Cd) in Al and discuss the micromechanism of the structural stability of Al-rich AlX alloys. The calculations are based on the generalized gradient approximation in the density-functional theory and employ the all-electron full-potential Korringa–Kohn–Rostoker Green's function method for point defects, which guarantees the correct embedding of the cluster of impurities and vacancies in an otherwise perfect crystal. We show: (1) the fundamental features of phase diagrams of these alloys, such as ordering and segregation, are understood by the sign of first-neighboring X–X interaction energies; (2) the structural stability of Al-rich AlX alloys such as L1 2 (Al 3Sc and Al 3Y), DO 22 (Al 3V and Al 3Nb), and Mackay icosahedron in AlMn quasicrystal, are understood qualitatively by using the medium-ranged and oscillating X–X interactions, due to the strong sp-d (Al–X) hybridization; (3) the strength and oscillating behavior of the medium-ranged X–X interaction energies are specified very well by the d-electron numbers of X impurities.