(561f) Incorporating Multi-Body Effects in SAFT: Impact on Model Patchy Colloid and Ion Hydration

Molecular association is important in describing thermodynamic behavior of complex fluid mixtures. These associating fluids find applications in various fields ranging from patchy colloids to electrolyte solutions to protein solvation etc.. The challenge in describing dense mixtures of associating fluids is due to multi-body effects. Recently an approach was developed to incorporate multi-body effects within the statistical associating fluid theory (SAFT)^1,2. This approach attempts to obtain the probabilities of packing patchy particles around a distinguished spherically symmetric solute in the gas-phase and on this basis constructs cluster partition functions. This approach provides a simplified way to obtain cluster partition functions for dense systems using gas phase packing probabilities for individual clusters. However, it fails to capture accurate behavior for highly dense systems.

            In this talk we will examine the reasons for this failure. Importantly we will highlight the need for the cluster partition functions to lead to the correct mean occupancy of the clustering volume. Imposing this constraint leads to revised cluster partition functions for the Hard-Sphere reference. Using this revised partition function in SAFT is then found to lead to a better prediction of structural and thermodynamic data for a mixture of spherically symmetric and patchy colloids.

1.         Marshall, B. D. & Chapman, W. G. Molecular theory for self assembling mixtures of patchy colloids and colloids with spherically symmetric attractions: The single patch case. J. Chem. Phys. 139, 104904 (2013).

2.         Marshall, B. D. & Chapman, W. G. Thermodynamic perturbation theory for self assembling mixtures of multi-patch colloids and colloids with spherically symmetric attractions. Soft Matter 9, 11346–11356 (2013).