SKM 2023 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 14: Development of Computational Methods: Thermodynamics and Local Chemistry, Electronic Structure
MM 14.4: Talk
Tuesday, March 28, 2023, 11:00–11:15, SCH A 251
Extracting free energies from local composition fluctuations in solids: Application on the atom probe data obtained from TAPSim simulations — •Jianshu Zheng1, Marvin Poul2, and Sebastian Eich1 — 1Institute of Materials Science, University of Stuttgart, Heisenbergstr. 3, D-70569 Stuttgart, Germany — 2Max-Planck-Institute für Eisenforschung GmbH, Max-Planck-Straße 1, D-40237 Düsseldorf, Germany
This work proposes a novel methodology to extract direct thermodynamic information, i.e. Gibbs free energies, from local composition fluctuations found in atom probe data based on statistical mechanics. The proof-of-concept is demonstrated with an exemplary simulated Cu–Ni alloy, which has first been equilibrated using Monto Carlo techniques with an embedded-atom potential and subsequently field evaporated by TAPSim[1]. It is shown that the variance of the local composition on the reconstructed data reveals a significant dependence on the size of the chosen (sub-) volume used for the evaluation, but nevertheless the extrapolation to an infinitely large volume unveils a remarkable link to the curvature of the Gibbs free energy. Given the composition range is explored at several points, the Gibbs excess free energy of mixing could be recovered in a CALPHAD-style parametrization. This methodology promises to improve the accuracy of thermodynamic information from direct atom probe measurements.
[1] C. Oberdorfer, S.M. Eich, G. Schmitz. Ultramicroscopy 128, (2013), 55.