Study of the Depolarized Light Scattering Spectra of Supercooled Liquids by a Simple Mode-Coupling Model

TL;DR

This paper uses a simplified mode-coupling model to analyze depolarized light scattering spectra of fragile supercooled liquids, achieving good experimental agreement and discussing the model's applicability and limitations.

Contribution

It introduces a minimal set of mode-coupling equations to fit experimental spectra of supercooled liquids, exploring the model's validity and parameter space.

Findings

Good fit between model and experimental spectra.

Identification of limitations in the model's effective vertices.

Discussion on the applicability of asymptotic predictions.

Abstract

By using simple mode coupling equations, we investigate the depolarized light scattering spectra of two so-called "fragile" glassforming liquids, salol (phenylsalicylate) and CKN (Ca_{0.4}K_{0.6}(NO_3)_{1.4}), measured by Cummins and coworkers. Nonlinear integrodifferential equations for the time evolution of the density-fluctuations autocorrelation functions are the basic input of the mode coupling theory. Restricting ourselves to a small set of such equations, we fit the numerical solution to the experimental spectra. It leads to a good agreement between model and experiment, which allows us to determine how a real system explores the parameter space of the model, but it also leads to unrealistic effective vertices in a temperature range where the theory makes critical asymptotic predictions. We finally discuss the relevance and the range of validity of these universal asymptotic predictions when applied to experimental data on supercooled liquids.