Solvent phase behavior and the interaction of uniform and patterned solutes

Isotropic and anisotropic hypernetted-chain (HNC) integral equation theories are used to obtain the interaction of solutes both near and far from the solvent liquid-vapor coexistence. Spherically symmetrical and chemically patterned (patched) solutes are considered, and the influences of particle and patch sizes are investigated. Solvophilic and solvophobic solutes (or patches) are examined. Near coexistence, in the solvophobic case drying like behavior occurs for solutes (patches) of sufficient size. This gives rise to relatively long ranged attractive forces that are strongly orientation dependent for the patched solute particles. We also report grand canonical Monte Carlo results for a pair of spherically symmetric solutes. This demonstrates that the anisotropic HNC theory gives qualitatively correct solvent structure in the vicinity of the solutes. Comparison with previous simulations also shows that the solute-solute potentials of mean force given by the anisotropic theory are more accurate (particularly at small separations) than those obtained using the isotropic method. (c) 2005 American Institute of Physics.