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Explaining the T,V-dependent dynamics of glass forming liquids: The cooperative free volume model tested against new simulation results

Explaining the T,V-dependent dynamics of glass forming liquids: The cooperative free volume model tested against new simulation results

Authors :
Ronald D. White
Jane E. G. Lipson
Source :
The Journal of Chemical Physics. 147:184503
Publication Year :
2017
Publisher :
AIP Publishing, 2017.

Abstract

In this article, we derive a rate model, the “cooperative free volume” (CFV) model, to explain relaxation dynamics in terms of a system’s free volume, Vfree, and its temperature, T, over widely varied pressure dependent conditions. In the CFV model, the rate a molecule moves a distance on the order of its own size is dependent on the cooperation of surrounding molecules to open up enough free space. To test CFV, we have generated extensive T,V dependent simulation data for structural relaxation times, τ, on a Kob and Andersen type Lennard-Jones (KA-LJ) fluid. The Vfree = V − Vhc values are obtained by estimating the limiting hard core volume, Vhc, through analysis of the KA-LJ PVT data. We provide the first simulation evidence that shows ln τ to be linearly proportional to 1/Vfree on isotherms, with T-dependent slopes, thus confirming our recent analysis of experimental systems. The linear relationship exhibited by the simulation data is further shown to occur at temperatures both above and below the tran...

Details

ISSN :
10897690 and 00219606
Volume :
147
Database :
OpenAIRE
Journal :
The Journal of Chemical Physics
Accession number :
edsair.doi.dedup.....a2663b53e7fe52ba2a25efaaaa90f6d1
Full Text :
https://doi.org/10.1063/1.5001714