Effective interaction between large spheres immersed into a multicomponent hard-sphere fluid

Abstract

An approach to study the effective interaction between two extremely large spheres, infinitely dilute, in a multicomponent hard-sphere fluid is presented. The proposed approach is an approximation that guarantees at least qualitative consistency with the experimental results for the interaction between two large solutes that is mediated by a background medium. The approach is developed to study the complex colloidal systems, i.e., extremely large (micronsized) spherical particles immersed in suspensions of the smaller (nanosized) colloid particles that are dissolved in a molecular solvents. Numerical results for the effective energy and force between two extremely large spheres in a one-component hard-sphere fluid (when only colloid particles are considered explicitly) and a two-component hard-sphere fluid (when both “solvent” particles and colloid particles are considered explicitly), are presented. The role of the discrete nature of the solvent on the interaction between two extremely large spheres immersed in a colloidal suspension is discussed. To account for the effect of colloid particle size polydispersity, calculations with four-component and ten-component hard-sphere fluids are performed. Using the Derjaguin approximation, the disjoining energy and pressure between two flat hard surfaces separated by a multicomponent hard-sphere fluid could be obtained.