STRUCTURE OF BINARY COLLOIDAL MIXTURES OF CHARGED AND UNCHARGED SPHERICAL-PARTICLES

The microstructure and thermodynamic quantities of binary mixtures of hard spheres and Yukawa particles are investigated by integral equation theories and Monte Carlo (MC) simulations. The Ornstein-Zernike equations for the partial pair correlation functions g(ij)(r) are solved with the Percus-Yevick, hypernetted-chain and Rogers-Young (RY) closure relations. The results obtained with the RY scheme are in very good agreement with MC data. From g(ij)(r) the partial static structure factors S(ij)(k), the number density structure factor S(NN)(k), the measured structure factor S(M)(k), and the isothermal compressibility are calculated for various compositions. It is found that the replacement of small amounts of charged by uncharged particles has a profound effect on the main peak of S(NN)(k), but it is of minor importance for the compressibility. The replacement of uncharged by charged particles, on the other hand, has strong effects on the compressibility, whereas the structure changes only weakly. Recent experimental results on mixtures of polystyrene and silica particles are discussed.