# Experimental observation of structural crossover in binary mixtures of colloidal hard spheres

## TL;DR

This study uses confocal microscopy and simulations to observe a structural crossover in binary colloidal hard sphere mixtures, revealing how particle size ratios influence local structure and network formation.

## Contribution

It provides experimental evidence and analysis of structural crossover phenomena in binary colloidal mixtures, linking microscopic structure to particle size ratios and packing fractions.

## Key findings

- Observed a change in dominant wavelength in pair correlation functions.
- Confirmed the structural crossover prediction with experimental data.
- Linked crossover to network extension of same-sized particle clusters.

## Abstract

Using confocal-microscopy we investigate the structure of binary mixtures of colloidal hard spheres with size ratio q=0.61. As a function of the packing fraction of the two particle species, we observe a marked change of the dominant wavelength in the pair correlation function. This behavior is in excellent agreement with a recently predicted structural crossover in such mixtures. In addition, the repercussions of structural crossover on the real-space structure of a binary fluid are analyzed. We suggest a relation between crossover and the lateral extension of networks containing only equally sized particles that are connected by nearest neighbor bonds. This is supported by Monte-Carlo simulations which are performed at different packing fractions and size ratios.