Structure and thermodynamics of a mixture of patchy and spherical colloids: a multi-body association theory with complete reference fluid information

TL;DR

This paper develops a multi-body association theory that accurately predicts the structure and thermodynamics of mixtures of patchy and spherical colloids by incorporating complete reference fluid information and occupancy statistics.

Contribution

It introduces a novel approach that integrates full reference fluid data into multi-body association modeling, improving predictions at high densities and strong associations.

Findings

Accurately predicts bonding states across various conditions.

Improves upon previous theories at high densities.

Uses enhanced sampling and quasichemical modeling for reference data.

Abstract

A mixture of solvent particles with short-range, directional interactions and solute particles with short-range, isotropic interactions that can bond multiple times is of fundamental interest in understanding liquids and colloidal mixtures. Because of multi-body correlations predicting the structure and thermodynamics of such systems remains a challenge. Earlier Marshall and Chapman developed a theory wherein association effects due to interactions multiply the partition function for clustering of particles in a reference hard-sphere system. The multi-body effects are incorporated in the clustering process, which in their work was obtained in the absence of the bulk medium. The bulk solvent effects were then modeled approximately within a second order perturbation approach. However, their approach is inadequate at high densities and for large association strengths. Based on the idea that the clustering of solvent in a defined coordination volume around the solute is related to occupancy statistics in that defined coordination volume, we develop an approach to incorporate the complete information about hard-sphere clustering in a bulk solvent at the density of interest. The occupancy probabilities are obtained from enhanced sampling simulations but we also develop a concise parametric form to model these probabilities using the quasichemical theory of solutions. We show that incorporating the complete reference information results in an approach that can predict the bonding state and thermodynamics of the colloidal solute for a wide range of system conditions.