Mixing effects for the structural relaxation in binary hard-sphere liquids

TL;DR

This study uses molecular dynamics simulations to examine how mixing different-sized hard spheres affects the glassy dynamics, revealing contrasting effects depending on size disparity.

Contribution

It provides detailed simulation data on binary hard-sphere mixtures, highlighting how mixing influences the structural relaxation in glass-forming liquids.

Findings

Large size disparity: increased small particles speed up dynamics.

Small size disparity: increased mixing slows down dynamics.

Results align with mode coupling theory predictions.

Abstract

We report extensive molecular-dynamics simulation results for binary mixtures of hard spheres for different size disparities and different mixing percentages,for packing fractions up to 0.605 and over a characteristic time interval spanning up to five orders in magnitude. We explore the changes in the evolution of glassy dynamics due to mixing and discover two opposite scenarios: for large size disparity, increasing the mixing percentage of small particles leads to a speed-up of long-time dynamics, while small disparity leads to a slowing down. These results agree with predictions based on the mode coupling theory for ideal glass transitions.