Depletion Potential Between Two Colloid Particles Immersed In A Hard-Core Yukawa Fluid

Yukawa potential function is widely used in the field of simulation of simple fluid and colloidal suspensions. With the development of colloidal sciences, the use of Yukawa potential becomes more and more important. In particular, the investigations on the Yukawa fluids and its mixtures in terms of density functional theory (DFT) have made a great progress. Accordingly, the model system based on the Yukawa potential function has become a hot topic and in recent years, which has attracted intense attentions.As is well known, depletion force between colloidal particles is an important type of inter-molecular force which originates from the mean-force potential mediated by a large number of solvents. In essence, the depletion force is induced by the increasing entropy of the system, and results in obvious effects on the aggregated structures of colloidal particles. In this paper, the method of DFT is applied to study the depletion force between colloidal particles immersed in a hard-core Yukawa(HCY) fluid. In detail, the Helmholtz free energy functional with the density distribution as functional variable is given, and then by minimizing the energy functional, the equilibrium density distribution can be obtained. Furthermore, the depletion potential and depletion force are evaluated, and on which the influences of the relevant factors are discussed. In this process, the fundamental-measure theory of Rosenfeld and its modified versions are used as a reference state.The dissertation of M.S. degree is mainly composed of three chapters:The first chapter:Introduction. A brief description of depletion interaction and colloidal systems is introduced in this chapter. At the same time, the development of DFT for classical fluid is also outlined.The second chapter:Density functional theory for depletion potential between two colloid particles in a hard-core Yukawa fluid. The depletion potential between two colloid particles immersed in a hard-core Yukawa fluid is investigated by the density functional theory for depletion potential proposed by Roth, Evans and Dietrich. An attempt is made to study the effects of several factors concerning colloid particles and solvent molecules on the depletion potential, which are the size ratio of the colloid particle to the solvent, the interaction between solvent molecules, the packing fraction of the solvent, and the interaction between the colloid particle and the solvent. By means of the depletion potential presented under various conditions, it is shown that the effects of these factors on the depletion potential are significant and this can provide some useful clues on regulating the interaction between colloid particles in related experiments.The third chapter:Perspective. As a result, some limitations and possible development in this topic are pointed out.