A density functional theory model of the SALR cluster fluid

Fluids with particles that interact through competing short-range attractive and long-range repulsive forces, known as SALR fluids, are often used to model complex mixtures involving proteins, colloids, polyelectrolytes etc. It is known that they can display a wide range of aggregation phenomena including a cluster fluid phase at low particle concentrations. While the cluster fluid phase can be simulated using relatively standard Monte Carlo and molecular dynamics methods, it has been more challenging to develop theoretical models of its thermodynamic behaviour. This is largely because of the difficulty of capturing its multi-scale properties. This work focusses on the development of a density functional theory (DFT) model of the SALR fluid with an emphasis on the cluster fluid phase. The few existing examples of such DFT models are reviewed and a novel weighted density functional model that avoids problems inherent in these existing models is proposed. This novel DFT model requires knowledge of bulk thermodynamic properties and the bulk pair direct correlation function at a reference state. This information can be provided by integral equation methods.