Associate Professor Jessica Krogstad and co-authors had their paper named an Editors’ Suggestion by Physical Review Materials. The study ties the characteristic thermal diffuse-scattering features in FCC metals to specific low-frequency lattice vibrations, then uses that understanding to propose measurement strategies, such as choosing particular crystal orientations, that separate thermal effects from the signal of chemical short-range order in complex alloys like stainless steels and high entropy alloys.
Written by Jackson Brunner
A new paper co-authored by Associate Professor Jessica Krogstad of the Department of Materials Science and Engineering at The Grainger College of Engineering, University of Illinois Urbana-Champaign, has been named an Editors' Suggestion by Physical Review Materials. The article, "Universal electron diffuse scattering in FCC alloys: A kinematic thermal diffuse-scattering analysis," was published October 13, 2026. Additional authors include Professor Emeritus Jian-Min Zuo of Illinois materials science and engineering, Professor Elif Ertekin of Illinois mechanical science and engineering, Po-Cheng Kung and Tianyu Su.
The calculated phonon dispersion curves of pure Ni highlights the low frequency transverse phonon. The curves are color-coded according to the direction of the phonon wave vector using the IPF color code so it’s straightforward to correlate this direction with the preferential scattering behavior along the same {111} directions. This gives rise to extra peaks in diffraction pattern (specifically the bright yellow-green reflections) that are often confused with signal from chemical short range ordering.
The study focuses on complex face-centered cubic (FCC) alloys, a catchall term for everything from austenitic stainless steels to high entropy alloys (HEA). Chemical short-range order, the non-random arrangement of different atoms on neighboring lattice sites, may contribute significantly to the properties of these materials. Electron diffuse scattering is one way to detect it, but signals from thermal diffuse scattering, which arise from atomic vibrations, can make the measurements difficult to interpret.
The authors revisited the theory behind thermal diffuse scattering and connected its characteristic features in FCC materials to the vibrational behavior of their crystal lattices, known as phonon dispersion relations. Simulations of pure nickel showed that commonly observed scattering features come from specific low-frequency lattice vibrations. Experiments on a medium-entropy alloy and an austenitic stainless steel confirmed that the same features appear in complex alloys, and temperature-dependent measurements verified their thermal origin.
The paper also identifies situations in which thermal diffuse scattering can interfere with the characterization of chemical short-range order, and it proposes strategies for avoiding the problem. One approach is to measure in crystal orientations where the thermal and chemical-order signals are distinctly separate in reciprocal space.
According to the authors, the work offers a transferable, physics-based approach for interpreting electron diffuse scattering in FCC metals and for designing measurements that isolate chemical short-range order from thermal effects.
Illinois Grainger Engineering Affiliations
Elif Ertekin is an Illinois Grainger Engineering associate professor of mechanical science and engineering. She is associate head for graduate programs and serves as director of mechanics programs. Ertekin holds the Andersen Faculty Scholar appointment.
Jessica Krogstad is an Illinois Grainger Engineering associate professor in the Department of Materials Science and Engineering. She is affiliated with the Materials Research Laboratory.
Jian-Min Zuo is an Illinois Grainger Engineering professor emeritus in the Department of Materials Science and Engineering.