Density functional theory for a macroion suspension

TL;DR

This paper develops a density functional theory for macroion suspensions considering electrostatic interactions, predicting phase separation and complex interfacial phenomena, with implications for understanding charge-density-wave formations.

Contribution

It introduces a novel DFT model for macroion suspensions incorporating electrostatic self-energy within a Debye-Huckel approximation, predicting phase behavior and structure factors.

Findings

Predicts liquid-liquid phase separation at low ionic strength.

Calculates interface structure and surface tension.

Shows structure factors obey Stillinger-Lovett conditions.

Abstract

A density functional theory for a macroion suspension is examined, where the excess free energy corresponds to the macroion self energy arising from the polarisation of the supporting electrolyte solution. This is treated within a linearised or Debye-Huckel approximation. The model predicts liquid-liquid phase separation at low ionic strength. The interface structure and surface tension between coexisting phases is calculated using a variational approximation. Results are also obtained for structure factors, which are shown to obey the Stillinger-Lovett moment conditions. As one approaches the critical points, the structure factors may diverge at a non-zero wavevector, indicating that the critical points could be replaced by charge-density-wave phases.