Regensburg 2016 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 4: Liquid and Amorphous Metals I: Glassy dynamics
MM 4.1: Vortrag
Montag, 7. März 2016, 10:15–10:30, H52
Experimental evidence for a dynamical crossover in liquid aluminium — •Franz Demmel1 and Christoph Morkel2 — 1ISIS Facility, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK — 2Physikdepartment E21, TU Munchen, 85748 Garching, Germany
The temperature dependence of the dynamic structure factor at next-neighbour distances has been investigated for liquid aluminium [1]. This correlation function is a sensitive parameter for changes in the local environment and its Fourier transform was measured in a coherent quasielastic neutron scattering experiment. The zero frequency amplitude decreases in a nonlinear way and indicates a change in dynamics around 1.4 Tmelting. From that amplitude a generalized viscosity can be derived which is a measure of local stress correlations on next-neighbour distances. The derived generalized longitudinal viscosity shows a changing slope at the same temperature range. At this temperature the freezing out of degrees of freedom for structural relaxation upon cooling sets in which can be understood as a precursor towards the solid state. Thermodynamic calculations for the solid state predicted an upper temperature stability limit for the solid phase which corresponds favourable with our observations. That crossover in dynamics of liquid aluminium shows the same signatures as previously observed in liquid rubidium and lead, indicating a universal character. [1] F. Demmel, A. Fraile, D. Szubrin, W.C. Pilgrim and C. Morkel, J.Phys.: Condens. Matter 27 455102 (2015)