Nature of nonanalytic chemical short-range order in metallic alloys

TL;DR

This paper demonstrates that chemical short-range order in metallic alloys is predominantly nonanalytic at the Gamma point, due to elastic anisotropy and long-range interactions, clarifying longstanding debates.

Contribution

It reveals the physical origin of nonanalytic SRO in alloys and suggests it as a universal feature to verify SRO in complex alloys.

Findings

SRO is mostly nonanalytic at Gamma in FCC alloys

Nonanalyticity arises from elastic anisotropy and long-range interactions

Nonanalytic SRO can serve as a signature for SRO in complex alloys

Abstract

Nonanalytic chemical short-range order (SRO) has long been observed in diffuse scattering experiments for metallic alloys. However, considerable debate surrounds the validity of these observations due to the unresolved nature of the nonanalyticity. Using prototypical face-centered cubic alloys as an example, here we demonstrate that SRO in metallic alloys is mostly nonanalytic at {\Gamma}. The nonanalyticity stems from the elastic anisotropy and long-range atomic interactions of the \emph{host} lattice. The physical insights substantially improve our understanding of chemical order in alloys and resolves the long-standing debate in the field. Nonanalytic SRO is expected to be general in alloys and the nonanalyticity may serve as a unique feature to verify the intensely debated existence of SRO in compositionally complex alloys.