Ordering tendencies in alloys and their microscopic origins from a first-principles theory of concentration waves

Abstract

Compositional, displacement, and magnetic pair-correlation functions in alloys are measured directly by diffuse scattering techniques. A first-principles theory of short-range order in high-temperature, disordered alloys has been developed and implemented that determines these correlation functions from the underlying local-density-functional electronic structure. Features in diffuse scattering experiments may be directly related to their electronic origins. Such a capability is not only important for interpreting experimental results but for understanding the microscopic origin of the system-dependent short-range order. Example applications are discussed in the Cu-Ni-Zn and Cu-Pt alloys, with emphasis on the importance of van-Hove states (i.e., the electronic states that give rise to van Hove singularities in the density of states). As a contrast, the origins for the magnetic and chemical short-range order in paramagnetic Cu-rich, Cu-Mn alloys, which are considered prototypical spin-glass systems, are also briefly discussed.