Suspension models soft sphere systems

The stability of colloidal systems consisting of charged particles can be essentially explained by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory [1-7]. According to this theory, the stability of a suspension of colloidal particles is determined by the balance between the electrostatic interaction and the van der Waals interaction between particles. A number of studies on colloid stability are based on the DLVO theory. In this chapter, as an example, we consider the interaction between lipid bilayers, which serves as a model for cell-cell interactions [8, 9]. Then, we consider some aspects of the interaction between two soft spheres, by taking into account both the electrostatic and van der Waals interactions acting between them. 

A collection of hard, identical spheres is the simplest possible model system that undergoes a first order phase transition. For low packing fractions the particles are in a liquid state, but when the packing fractions exceeds a value of 49.4% a ordered solid state becomes more stable. This was first shown in computer simulations by Hoover and Ree [27] in 1968. The experimental realization of a colloidal suspension that closely mimics the phase behavior of hard spheres followed about 20 years later and was a milestone in soft matter physics [28, 29]. More recently the phase transition kinetics of hard sphere colloids has been studied extensively in experiments [5, 30, 31]. However as mentioned in the introduction the interpretation of the data with CNT was rather indirect. 

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