Dresden 2026 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 15: Phase Transformations I
MM 15.5: Talk
Tuesday, March 10, 2026, 15:00–15:15, SCH/A215
Grain boundary thermodynamics away from idealized boundaries: How line defects affect stability — •Tobias Brink1, Swetha Pemma1,2, Lena Langenohl1, Saba Saood1, Yoonji Choi1, Rebecca Janisch2, Christian H. Liebscher2, and Gerhard Dehm1 — 1MPI for Sustainable Materials, Düsseldorf, Germany — 2Ruhr-Universität Bochum, Germany
The concept of grain boundary (GB) phases (or “complexions”) was developed to describe how the atomic structure and/or chemistry of GBs depend on external conditions, such as temperature or chemical potential. Analogous to bulk phases, GB phases also affect material properties. Even in the case of pure metals, structural GB transformations impact diffusivity and GB mobility. Simulation studies often concentrate on special, symmetric boundaries, which are easy to describe. It is unlikely, however, that their behavior can be generalized to the variety of imperfect GBs in a real polycrystal.
Here, we use atomistic simulations with empirical potentials to investigate thermodynamics of asymmetric GBs in Cu. Symmetric ⟨111⟩ tilt boundaries exhibit two GB phases. These also exist in asymmetric GBs, but contain multiple line defects (disconnections) that enable the deviation from the symmetric GB plane. We found the same defects in thin film samples using scanning electron transmission microscopy. Most importantly, their presence alters the thermodynamic stability of the two GB phases, even for very small deviations from the symmetric GB. We conclude that defects of defects have to be considered in interface thermodynamics.
Keywords: Asymmetric grain boundaries; Interface phases; Faceting; Line defects