Interaction site fluids applications

We have chosen to focus almost entirely on the theoretical techniques themselves and on applications that test the accuracy of these techniques. Thus, we will generally refer to the rather large literature on the study of interaction site fluids via Monte Carlo and molecular dynamics simulations only as it impinges directly upon the theoretical developments. We have also taken advantage of the availability of review articles by Chandler and Rossky in limiting our discussion of applications such as the calculation of specific liquid structures and chemical equilibrium, which were described in detail in those articles. 

In this section, we review some of the important formal results in the statistical mechanics of interaction site fluids. These results provide the basis for many of the approximate theories that will be described in Section III, and the calculation of correlation functions to describe the microscopic structure of fluids. We begin with a short review of the theory of the pair correlation function based upon cluster expansions. Although this material is featured in a number of other review articles, we have chosen to include a short account here so that the present article can be reasonably self-contained. Cluster expansion techniques have played an important part in the development of theories of interaction site fluids, and in order to fully grasp the significance of these developments, it is necessary to make contact with the results derived earlier for simple fluids. We will first describe the general cluster expansion theory for fluids, which is directly applicable to rigid nonspherical molecules by a simple addition of orientational coordinates. Next we will focus on the site-site correlation functions and describe the interaction site cluster expansion. After this, we review the calculation of thermodynamic properties from the correlation functions, and then we consider the calculation of the dielectric constant and the Kirkwood orientational correlation parameters. 

As we mentioned in the opening paragraph, thermodynamic perturbation theory has been used in two contexts in applications to interaction site fluids. In this section, we will describe efforts to treat the thermodynamics and structure of interaction site fluids in terms of a perturbation expansion where the reference system is a fluid in which the intermolecular forces are spherically symmetric. In developing thermodynamic perturbation theories, it is generally necessary to choose both a reference system and a function for describing the path between the reference fluid and the fluid of interest. The latter choice is usually made between the pair potential and its Boltzmann factor. Thus one writes either... 

Kristof, T. Liszi, J., Application of a new Gibbs ensemble Monte Carlo method to site-site interaction model fluids, Mol. Phys. 1997, 90, 1031-1034... 

A further possibility is the formation of liquid crystals on contact with body fluids at the site of application. The initially applied drug solution interacts with body fluids such as plasma, tears, or skin lipids and undergoes a phase transition into a mono-or multiphasic system of liquid crystals (Fig. 15). For example, oily solutions of reverse micellar solutions of phospholipids, which solubilize additional drug, trans-... 

There have been numerous applications of the RAM theory to both interaction site as well as other models of molecular fluids. There is... 

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. 

One of the most active areas of research in the statistical mechanics of interfacial systems in recent years has been the problem of freezing. The principal source of progress in this field has been the application of the classical density-functional theories (for a review of the fundamentals in these methods, see, for example, Evans ). For atomic fluids, such apphcations were pioneered by Ramakrishnan and Yussouff and subsequently by Haymet and Oxtoby and others (see, for example, Baret et al. ). Of course, such theories can also be applied to the vapor-liquid interface as well as to problems such as phase transitions in liquid crystals. Density-functional theories for these latter systems have not so far involved use of interaction site models for the intermolecular forces. 

Nanoparticles interact with fluids, cells, and tissues. Therefore, checking the toxicity of nanoparticles is a necessity. At the site of final retention in the target organs, nanoparticles may tri er mediators, which then may activate inflammatory or immunological responses. With such reasons, designing the biopol3mier-based nanoparticles with the specific sizes is one of the most important criteria for delivery carrier application. Particle shape, surface charge, and surface feature also play roles in intercellular deliveiy... 

The reference interaction site model (RISM) theory of Chandler and Andersen [9, 11, 10] is an extension of the theory of monatomic liquids. In RISM theory, each molecule is envisioned as a collection of spherically symmetric interaction sites. In most applications of RISM theory to small molecule liquids. Chandler and coworkers [9, 11, 12, 13, 10] modeled interaction sites as overlapping hard spheres. The primary difference between RISM theory and monatomic liquid theory is that the correlations can be propagated intramolecularly as well as intermolecularly. Chandler and Andersen generalized the OZ equation as follows for a single component fluid in Fourier space... 

The difference between and the full renormalized potential is a well-behaved function that is evaluated numerically. The interest in the renormalization procedure is now mainly a theoretical one as formal results regarding screening and other thermodynamic parameters can be obtained this way. Results applicable to both pure one-component fluids or mixtures can be obtained. The numerical solution of integral equations, such as the SSOZ and CSL equations, for sites with charge interactions should no longer use the renormalization method but rather the method we are about to describe. 

The structure of site-site molecular fluids can now be obtained on a routine basis using either the SSOZ equation or CSL equation and an associated closure. The numerical method described in Section IV.C is generally applicable. It is fair to say that the results obtained are in general not as accurate as those obtained for atomic fluids using the analogous method. As a result we will not attempt to review the literature but refer the reader to the review by Rossky which deals with structure exhaustively. We will, however, look at some general structural questions such as, why do strong dipolar interactions have little effect on the structure when quadrupolar interactions (such as those in Br2) do effect the structure. These empirical observations have been made many times, but it was not until the work of Fraser et al. that even a qualitative explanation of these effects was possible. 

For REVS applications using clinical samples, it is necessary to detect viruses in more complex biological fluids, such as serum or cerebrospinal fluid, which contain large quantities of proteins. To test the suitability of the REVS technique for use in complex specimens, HSV samples were diluted in calf serum. Peaks were observed in the region of 7.1 V (Fig. 12). The fact that multiple, distinct peaks can be observed in serum may be due to partial non-specific blocking of some antibody binding sites by serum proteins, which could lead to more variations in the number of interactions between the virus and the surface than is the case in PBS. 

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