Homogeneous fluids dielectric properties

In this section, we will review some of the results obtained for homogeneous fluids. The focus of the section strongly reflects the author s particular interest rather than a complete review of all work done in this area. To a large extent, we will concentrate on aspects that have not been reviewed previously, or on areas that developed since those reviews. The first section deals with the influence of electrostatic interactions on the structure factor, and we stress the decoupling of dipole-dipole interactions from the structure factor, although there is a strong effect on particular g y r) s. In Section V.B we consider the dielectric constant obtained from the CSL equation with particular reference to the influence of shape forces in the dielectric properties. Section V.C considers the application of interaction site theories to calculate thermodynamic properties and fluid phase equilibria. 

Ultimately physical theories should be expressed in quantitative terms for testing and use, but because of the complexity of liquid systems this can only be accomplished by making severe approximations. For example, it is often necessary to treat the solvent as a continuous homogeneous medium characterized by bulk properties such as dielectric constant and density, whereas we know that the solvent is a molecular assemblage with short-range structure. For an example of this tool with supercritical fluids see Ting et al., 1993. 

Consider a spherical point dipole solute molecule with a dipole moment, p, at infinite dilution in a spherical container of supercritical fluid. With a continuum assumption, the fluid s electrical properties may be represented by a homogeneous dielectric constant, e. The inhomogeneous field of the dipole polarizes the fluid which reacts and gives rise to a field, R, at the dipole. R will be proportional to p as long as no saturation effects occur. 

Among homogeneous ER fluids, there are systems that show an anomalous ER efiect. Strong dielectric, low molecular weight liquid crystals [48] and polar polymer solutions [49, 50] exhibit a negative ER effect, in which the viscosity and dynamic mechanical properties decrease. 

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