Dresden 2026 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 41: Development of Calculation Methods II

MM 41.2: Talk

Friday, March 13, 2026, 10:30–10:45, SCH/A251

Clarifying the existence of a miscibility gap in platinum-palladium alloys via compositional fluctuations — •Florian Groll, Sebastian Eich, and Guido Schittz — Institute of Materials Science, Stuttgart, Germany

In materials science, the Gibbs free energy is of central importance for calculating phase diagrams. CALPHAD assessments require extensive experimental measurements and data obtained from well-equilibrated samples. For alloy systems with extremely low diffusion coefficients, achieving such equilibrium can be very time-consuming or practically impossible. Because this approach relies only on nanometer-scale equilibration, it provides a significantly more efficient route to the determination of CALPHAD parameters for systems with extremely slow diffusion. The palladium-platinum system is a well-known example for those kind of systems with unknown miscibility gap. In this study, we determine the Pd*Pt phase diagram by extracting the curvature of the Gibbs free energy from local composition fluctuations in the solid state using fluctuation theory. The experimental data needed for applying the local fluctuation theory are obtained from atom probe tomography, and the phase diagram is subsequently calculated.

Keywords: Pd–Pt alloys; Local composition fluctuations; Fluctuation theory; Atom probe tomography; Phase diagram