Wetting-induced effective interaction potential between spherical particles

Using a density-functional-based interface displacement model, we determine the effective interaction potential between two spherical particles which are immersed in a homogeneous fluid such as the vapor phase of a one-component substance or the A-rich liquid phase of a binary liquid mixture composed of A and B particles. If this solvent is thermodynamically close to a first-order fluid-fluid phase transition, the spheres are covered with wetting films of the incipient bulk phase, i.e., the liquid phase or the B-rich liquid, respectively. Below a critical distance between the spheres their wetting films snap to a bridgelike configuration. We determine phase diagrams for this morphological transition, and analyze its repercussions on the effective interaction potential. Our results are accessible to various types of force microscopy and scattering experiments, and may be relevant to flocculation in colloidal suspensions.