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Title: Correlation between dynamic slowing down and local icosahedral ordering in undercooled liquid Al{sub 80}Ni{sub 20} alloy

We use ab initio molecular dynamics simulations to study the correlation between the local ordering and the dynamic properties of liquid Al{sub 80}Ni{sub 20} alloy upon cooling. Our results evidence a huge increase of local icosahedral ordering (ISRO) in the undercooled regime which is more developed around Ni than Al atoms. We show that ISRO has a strong impact on self-diffusion coefficients of both species and is at the origin of their crossover from Arrhenius to non-Arrhenius behavior around a crossover temperature T{sub X} = 1000 K, located in the undercooled region. We also clearly identify that this temperature corresponds to the development of dynamic heterogeneities and to the breakdown of the Stokes-Einstein relation. At temperatures below this crossover, we find that the behavior of the diffusion and relaxation dynamics is mostly incompatible with predictions of the mode-coupling theory. Finally, an analysis of the van Hove function indicates that the crossover temperature T{sub X} marks the onset of a change in the diffusion mechanism from a normal flow to an activated process with hopping. From these results, the glass-forming ability of the alloy is discussed.
Authors:
;  [1]
  1. Sciences et Ingénierie des Matériaux et Procédés, UMR CNRS 5266, Grenoble Université Alpes, BP 75, 38402 Saint-Martin d’Hères Cedex (France)
Publication Date:
OSTI Identifier:
22493585
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 8; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALUMINIUM BASE ALLOYS; ATOMS; COUPLING; GLASS; LIQUIDS; MOLECULAR DYNAMICS METHOD; NICKEL ALLOYS; RELAXATION; SELF-DIFFUSION; SLOWING-DOWN; STOKES LAW; TEMPERATURE DEPENDENCE