Stochastic Generation of Particle Structures with Controlled Degree of Heterogeneity

TL;DR

This paper analyzes how the void expansion method (VEM) can generate particle microstructures with controllable heterogeneity, matching colloidal structures, by adjusting the void-particle ratio during simulation.

Contribution

It demonstrates that VEM can efficiently produce microstructures with a tunable degree of heterogeneity, comparable to colloidal suspensions, across a range of volume fractions.

Findings

VEM allows continuous control of heterogeneity for volume fractions 0.4-0.55.

VEM-generated structures cover a broad heterogeneity range similar to colloidal suspensions.

VEM is effective for stochastic reproduction of colloidal microstructures.

Abstract

The recently developed void expansion method (VEM) allows for an efficient generation of porous packings of spherical particles over a wide range of volume fractions. The method is based on a random placement of the structural particles under addition of much smaller "void-particles" whose radii are repeatedly increased during the void expansion. Thereby, they rearrange the structural particles until formation of a dense particle packing and introduce local heterogeneities in the structure. In this paper, microstructures with volume fractions between 0.4 and 0.6 produced by VEM are analyzed with respect to their degree of heterogeneity (DOH). In particular, the influence of the void- to structural particle number ratio, which constitutes a principal VEM-parameter, on the DOH is studied. The DOH is quantified using the pore size distribution, the Voronoi volume distribution and the density-fluctuation method in conjunction with fit functions or integral measures. This analysis has revealed that for volume fractions between 0.4 and 0.55 the void-particle number allows for a quasi-continuous adjustment of the DOH. Additionally, the DOH-range of VEM-generated microstructures with a volume fraction of 0.4 is compared to the range covered by microstructures generated using previous Brownian dynamics simulations, which represent the structure of coagulated colloidal suspensions. Both sets of microstructures cover similarly broad and overlapping DOH-ranges, which allows concluding that VEM is an efficient method to stochastically reproduce colloidal microstructures with varying DOH.