Regensburg 2004 – wissenschaftliches Programm

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M: Metallphysik

M 2: Flüssige und amorphe Metalle I

M 2.1: Vortrag

Montag, 8. März 2004, 10:15–10:30, H16

Medium range order in molten intermetallic alloys: Dynamics of the prepeak — •Sandro Jahn¹ and Jens-Boie Suck² — ¹PTCL, Oxford University, South Parks Road, Oxford OX1 3QZ, UK — ²Institut of Physics, Materials Research and Liquids, TU Chemnitz, 09107 Chemnitz

In molten intermetallic alloys of the Zintl-type a structural feature is observed in the static structure factor S(Q) at Q around 10 nm⁻¹. This so called prepeak represents correlations on length scales beyond the nearest neighbour atomic distance, which occur as a result of charge transfer between the different species and the formation of ionic and partly covalent bonds. Computer simulations show the persistence of polyanionic networks in the liquid state. Here we present first dynamic measurements around the prepeak region for three different alloy systems, Na-Sn, Rb-Sb and K-Sb, using cold neutron quasielastic scattering. From the width of the quasielastic line we can estimate the lifetime of the structures responsible for the prepeak. The decay of the correlation function is slowed down considerably in the prepeak region, but the actual decay time depends strongly on the size of the ions.