Void structure and cage dynamics in concentrated suspensions

TL;DR

This study investigates the structure and dynamics of concentrated colloidal suspensions using void space analysis, revealing how local heterogeneity influences nucleation and cage dynamics during crystallization.

Contribution

It introduces the concept of remoteness to analyze void space and demonstrates its effectiveness in studying crystallization and cage dynamics in dense suspensions.

Findings

Remoteness helps identify nucleation at higher local concentrations.

Crystallization transforms neighbor set remoteness distributions to exponential.

Local volume fraction fluctuations reveal cage dilation and compression.

Abstract

We analyse structure and dynamics in simulated high-concentration hard sphere colloidal suspensions by means of calculations based on the void space. We show that remoteness, a quantity measuring the scale of spaces, is useful in studying crystallization, since ordering of the particles involves a change in the way empty space is distributed. Calculation of remoteness also allows breakdown of the system into mesoscopic neighbor sets: statistics of mean remoteness and local volume fraction in these neighbor sets reveal that nuclei are formed at locally higher concentration, i.e. nucleation involves increased heterogeneity of the system. Full crystallization results in the transformation of the neighbor set mean remoteness distribution to an exponential form. The temporal fluctuation of local volume fractions in neighbor sets reveals significant details of dynamics, including abrupt dilations and compressions of local regions: leading to a clearer picture of the physical components of 'cage' dynamics in the colloidal glass.