Regensburg 2007 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 9: Liquid and amorphous materials III

MM 9.2: Vortrag

Montag, 26. März 2007, 15:00–15:15, H4

Negative entropy of mixing in computer simulated bulk glass forming AlxNi1-xZr60 melts — Mohammed Guerdane and •Helmar Teichler — Inst. f. Materials Physics, University of Göttingen, D-37077 Göttingen

For multi-component random systems, the ideal solution model predicts positive entropy of mixing, reflecting the increase of configuration space by exchange of chemically different particles. Glass forming melts are usually far from being random. Regarding this, AlxNi1-xZr60 is known to have marked short- and intermediate-range order. The former is characterized by icosahedral neighbour cages around Al- and by trigonal-prismatic ones around Ni-atoms, the latter by chain arrangements of Al- and of Ni-cages (M. Guerdane and H. Teichler, PRE 65, 014203 (2001)). Here the question arises whether in AlxNi1-xZr60 melts the entropy of mixing is positive, due to a gain in configuration space by particle exchange, or negative, due to a decreased density of low-energy states in the complex liquid at mid-concentrations. Concerning this, we report molecular dynamics results for AlxNi1-xZr60 melts based on the adiabatic switching approach. They show strong negative entropy of mixing along the quasi-binary line, i.e., predominance of enthalpic over entropic effects in this bulk glass forming liquid. (Supported by DFG SPP 1120 *Phase Transformations in Multi-Component Melts*.)