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MM: Fachverband Metall- und Materialphysik

MM 59: Phase Transitions I

MM 59.2: Vortrag

Donnerstag, 25. März 2010, 14:15–14:30, H5

Bulk and near-surface microstructure of Ni-23 at.% Pt — •Markus Engelke¹, Bernd Schönfeld¹, and Andrei Ruban² — ¹LMPT, Department of Materials, ETH Zurich — ²KTH Stockholm, Sweden

Diffuse x-ray scattering was taken from bulk single-crystalline Ni-23.2 at.% Pt. The sample was aged at 923 K to set up a state of thermal equilibrium. Using separation techniques, short-range order and static atomic displacements were determined. In comparison with a previously performed study from the same sample to characterize the near-surface microstructure by grazing incidence diffraction, differences are noted: they mainly refer to the static atomic displacements, being smaller in magnitude in the bulk than in the near-surface region. Effective pair interaction parameters show a dominant nearest-neighbor parameter, larger than that on the Pt-rich side. This is reflected in different order-disorder transition temperatures for Ni with 25 and 75 at.% Pt (L1₂ structure). First-principles electronic structure calculations support these findings.