Regensburg 2007 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 28: Intermetallic phases I

MM 28.2: Vortrag

Donnerstag, 29. März 2007, 10:30–10:45, H16

On the thermodynamics of the Pt-Rh alloy: Lattice Monte Carlo simulations using a refined BOS mixing model — •Johan Pohl and Karsten Albe — TU Darmstadt, Fachbereich Material- und Geowissenschaften, Petersenstr. 23, D-64287 Darmstadt

The phase diagram of Pt-Rh printed in most collections of phase diagrams shows a broad miscibility gap. Recent theoretical and experimental studies in contrast indicate that this gap does not exist, but that stable low-temperature ordered phases are present. We calculated the critical temperatures of the theoretically predicted ordered structures and short range order at high temperatures by means of Lattice Monte Carlo simulations using a refined BOS mixing model. This model is able to accurately reproduce the enthalpy of mixing at finite temperatures obtained with the cluster expansion formalism and subsequent cluster variation. Given its simplicity, our model allows computationally more efficient Monte Carlo simulations than the cluster expansion and may also be used for the modelling of nanoparticles. We obtained configurational free energies by thermodynamic integration in the semi-grand canonical ensemble for the different solid solution phases and the implications on phase stability will be presented.