ABSTRACT
In this chapter, we give a quick look at the theoretical description of more complex systems, such as fluids near the critical point, electrolyte solutions, liquid metals, polymers, colloids, and protein solutions. The complexity of the fluids near the critical point arises from the large-scale fluctuations involved. Most of the theories analyzed in Chapters 4, 6 through 9 fail to provide accurate results near the critical point unless appropriate corrections are introduced, as will be explained in Section 10.1. In the remaining systems considered in this chapter, the complexity arises from the interactions involved. In particular, in the mixtures discussed in Sections 10.3 and 10.4 of this chapter, the complexity is partially due to the large asymmetric sizes of the components of the mixtures. In these complex mixtures, the problem is largely simplified by introducing an effective potential allowing to map the mixture onto an effective one-component fluid. Therefore, a considerable part of Section 10.3 is devoted to the introduction of several effective potential models. The application of the effective one-component approach to a class of particularly challenging systems, namely, globular proteins in solution, is illustrated in Section 10.4.
