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Heterogeneous diffusion, viscosity, and the Stokes-Einstein relation in binary liquids

Schober, H. R. and Peng, Hailong (2016) Heterogeneous diffusion, viscosity, and the Stokes-Einstein relation in binary liquids. Physical Review E, 93, 052607. American Physical Society. DOI: 10.1103/PhysRevE.93.052607 ISSN 1539-3755

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We investigate the origin of the breakdown of the Stokes-Einstein relation (SER) between diffusivity and viscosity in undercooled melts. A binary Lennard-Jones system, as a model for a metallic melt, is studied by molecular dynamics. A weak breakdown at high temperatures can be understood from the collectivization of motion, seen in the isotope effect. The strong breakdown at lower temperatures is connected to an increase in dynamic heterogeneity. On relevant time scales some particles diffuse much faster than the average or than predicted by the SER. The van Hove self-correlation function allows one to unambiguously identify slow particles. Their diffusivity is even less than predicted by the SER. The time span of these particles being slow particles, before their first conversion to be a fast one, is larger than the decay time of the stress correlation. The contribution of the slow particles to the viscosity rises rapidly upon cooling. Not only the diffusion but also the viscosity shows a dynamically heterogeneous scenario. We can define a “slow” viscosity. The SER is recovered as the relation between slow diffusivity and slow viscosity.

Item URL in elib:https://elib.dlr.de/104548/
Document Type:Article
Title:Heterogeneous diffusion, viscosity, and the Stokes-Einstein relation in binary liquids
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Schober, H. R.h.schober (at) fz-juelich.deUNSPECIFIED
Peng, Hailonghailong.peng (at) dlr.deUNSPECIFIED
Date:16 May 2016
Journal or Publication Title:Physical Review E
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
DOI :10.1103/PhysRevE.93.052607
Page Range:052607
Publisher:American Physical Society
Keywords:glass transition, Stokes Einstein relation, viscosity, diffusion
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Research under Space Conditions
DLR - Research area:Raumfahrt
DLR - Program:R FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):R - Vorhaben Materialwissenschaftliche Forschung (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Physics in Space
Deposited By: Voigtmann, Dr.rer.nat. Thomas
Deposited On:09 Jun 2016 06:51
Last Modified:18 Nov 2020 04:23

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