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M: Metallphysik

M 9: Symposium Complex Metallic Alloys II

M 9.2: Vortrag

Freitag, 4. März 2005, 15:30–15:45, TU H1058

The atomic pair distribution function (PDF) as a nano-scale structure probe for CMA — •Stefan Brühne¹, Eckhard Uhrig¹, Michael Feuerbacher², and Wolf Assmus¹ — ¹Physikalisches Institut, Johann Wolfgang Goethe-Universität, Robert-Mayer-Str. 2-4, D-60054 Frankfurt am Main — ²Institut für Mikrostrukturforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich

The local atomic structure of any condensed matter is accessible via the atomic pair distribution function (PDF) from powder diffraction. We recently succeeded in unraveling the local structure of some icosahedral Mg-Zn-RE (RE = Y and Ho) alloys from in-house X-ray experiments in a sphere of 5.4 nm. Synchrotron data yield better resolved PDFs though they result in the same structural units of ∼1.5 nm in diameter. The method also applies well to the investigation of inherent disorder of Complex Metallic Alloys (CMA). The local structures of the Mg-Zn binaries MgZn₂ (hP12) and Mg₄Zn₇ (mC110) are discussed: The different length scales of the local structures vs. large translations become directly visible. The PDF of β-Al₃Mg₂ (cF1832-664, a≈ 2.8 nm), one of the most complex CMA in terms of unit cell dimension and atomic disorder, is examined. PDF will serve as a probe for monitoring the local atomic structure in the course of tailoring CMA structures w.r.t. their physical and mechanical properties.