Cluster formation in fluids with competing short-range and long-range interactions.
We investigate the low density behaviour of fluids that interact through a short-ranged attraction together with a long-ranged repulsion (SALR potential) by developing a molecular thermodynamic model. The SALR potential is a model of effective solute interactions where the solvent degrees of freedom are integrated-out. For this system, we find that clusters form for a range of interaction parameters where attractive and repulsive interactions nearly balance, similar to micelle formation in aqueous surfactant solutions. We focus on systems for which equilibrium behaviour and liquid-like clusters (i.e., droplets) are expected, and find in addition a novel coexistence between a low density cluster phase and a high density cluster phase within a very narrow range of parameters. Moreover, a simple formula for the average cluster size is developed. Based on this formula, we propose a non-classical crystal nucleation pathway whereby macroscopic crystals are formed via crystal nucleation within microscopic precursor droplets. We also perform large-scale Monte Carlo simulations, which demonstrate that the cluster fluid phase is thermodynamically stable for this system.
Institute of Materials and Processes, School of Engineering, University of Edinburgh, Edinburgh EH9 3JL, United Kingdom.
Martin B
MB
Sweatman
Institute of Materials and Processes, School of Engineering, University of Edinburgh, Edinburgh EH9 3JL, United Kingdom.
Rui
R
Fartaria
Department of Chemical and Process Engineering, University of Strathclyde, Glasgow G1 1XJ, United Kingdom.
Leo
L
Lue
D003102:Colloids / Q000737:chemistry; D008823:Micelles; D009010:Monte Carlo Method; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D012996:Solutions; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013816:Thermodynamics
D003102:Colloids; D008823:Micelles; D011108:Polymers; D012996:Solutions; D013501:Surface-Active Agents