Breakdown of the Stokes-Einstein relation in two, three, and four dimensions

Sengupta, Shiladitya and Karmakar, Smarajit and Dasgupta, Chandan and Sastry, Srikanth (2013) Breakdown of the Stokes-Einstein relation in two, three, and four dimensions. In: Journal of Chemical Physics, 138 (12). 548_1-548_14.

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Abstract

The breakdown of the Stokes-Einstein (SE) relation between diffusivity and viscosity at low temperatures is considered to be one of the hallmarks of glassy dynamics in liquids. Theoretical analyses relate this breakdown with the presence of heterogeneous dynamics, and by extension, with the fragility of glass formers. We perform an investigation of the breakdown of the SE relation in 2, 3, and 4 dimensions in order to understand these interrelations. Results from simulations of model glass formers show that the degree of the breakdown of the SE relation decreases with increasing spatial dimensionality. The breakdown itself can be rationalized via the difference between the activation free energies for diffusivity and viscosity (or relaxation times) in the Adam-Gibbs relation in three and four dimensions. The behavior in two dimensions also can be understood in terms of a generalized Adam-Gibbs relation that is observed in previous work. We calculate various measures of heterogeneity of dynamics and find that the degree of the SE breakdown and measures of heterogeneity of dynamics are generally well correlated but with some exceptions. The two-dimensional systems we study show deviations from the pattern of behavior of the three-and four-dimensional systems both at high and low temperatures. The fragility of the studied liquids is found to increase with spatial dimensionality, contrary to the expectation based on the association of fragility with heterogeneous dynamics.

Item Type:	Journal Article
Publication:	Journal of Chemical Physics
Publisher:	American Institute of Physics
Additional Information:	Copyright of this article belongs to American Institute of Physics.
Keywords:	Diffusion; Electric Breakdown; Free Energy; Viscosity; Vitreous State; Vitrification
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	04 Jun 2013 11:43
Last Modified:	04 Jun 2013 11:43
URI:	http://eprints.iisc.ac.in/id/eprint/46524

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