Abstract
We previously investigated the lifetime of dynamical heterogeneity in supercooled liquids in terms of a four-point, three-time density correlation function via molecular dynamics simulations [Phys. Rev. E 79 (2009) 060501(R); J. Chem. Phys. 133 (2010) 044511]. In this letter, we examine the physical role of the lifetime of dynamicsl heterogeneity in the violation of the Stokes–Einstein (SE) relation by calculating the frequency-dependent viscosity and self-diffusion constant. Our results demonstrate that the SE relation holds up to the time scale at which the non-Gaussian parameter is maximum. Large violations of the SE relation are characterized by time scales longer than the lifetime of the dynamical heterogeneity in highly supercooled liquids.
Highlights
We previously investigated the lifetime of dynamical heterogeneity in supercooled liquids in terms of a four-point, three-time density correlation function via molecular dynamics simulations [Phys
We have comprehensively investigated the temporal structure of dynamical heterogeneity.31,32) In the study, we argue that in order to quantify the lifetime hetero, it is essential to investigate how the correlated particle motions decay with time
The same discussion has been made in a recent work.27) We note that our numerical result is relevant to an experiment in colloidal glasses for detecting the contribution of dynamical clusters in the frequency-dependent shear modulus.34) Recent singlemolecule experiments for detecting the local mobility of probe molecules dispersed in glassy materials have another relevance to our simulations.35–38) In these experiments, the lifetime of dynamical heterogeneity is evaluated from the exchange time between mobile and immobile regions, which is found to be much slower than the structural relaxation time near the glass transition temperature
Summary
We previously investigated the lifetime of dynamical heterogeneity in supercooled liquids in terms of a four-point, three-time density correlation function via molecular dynamics simulations [Phys. We examine the physical role of the lifetime of dynamicsl heterogeneity in the violation of the Stokes–Einstein (SE) relation by calculating the frequency-dependent viscosity and self-diffusion constant.
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