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Time-dependent four-point density correlation functions in supercooled liquids

S. C. Glotzer·V. N. Novikov·T. B. Schroeder
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Abstract

Dynamical heterogeneity and the decoupling of diffusion and structural relaxation in a supercooled liquid is investigated in terms of a time-dependent, fourth-order density correlation function. The generalized susceptibility $χ_4(t)$ corresponding to this correlation function has a maximum at an intermediate time $t_4^*$, and both $t_4^*$ and $χ_4(t_4^*)$ grow strongly with decreasing temperature. We show that the main contribution to $χ_4(t)$ arises from spatial correlations between temporarily localized (``caged'') particles. We compare $χ_4(t)$ with a generalized susceptibility $χ_M(t)$ related to a correlation function of squared particle displacements, and show that while $t_4^*$ is roughly proportional to the $α$-relaxation time, $t_M^*$ is proportional to the inverse of the self-diffusion coefficient.

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S. C. Glotzer, V. N. Novikov, T. B. Schroeder. 1999-10-14. Time-dependent four-point density correlation functions in supercooled liquids. https://arxiv.org/abs/cond-mat/9909113

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