Reference interaction site theory extended

The original OZ equation can be applied only to liquids composed of spherically symmetrical particles, namely atoms. Chandler and Andersen proposed one of the possible extensions to treat general polyatomic cases, referred to as the reference interaction site model (RISM) or site-site OZ (SSOZ) theory [4], This has been further extended by Hirata and Rossky to be applicable to polar molecules such as water [5], In the RISM theory,... 

The central problem in the liquid state theory of polymers is the determination of a)ay(r) and gay(r). This cannot be done exactly (except by a many-molecule computer simulation) and many approximate schemes have been proposed which extend theories for simple liquids to polymers. Perhaps the most widely used approach is that of Curro and Schweizer, " known as the polymer reference interaction site model (PRISM) theory which is based on the RISM theory of Chandler and Andersen, I will describe this approach and compare its predictions to computer simulations and other theories. 

The basic approach of chemical theory to surface science is to model a surface with a cluster of a finite number of atoms, with one or more adsorbate atoms or molecules bonded to various sites on the cluster. In parallel with the chemical theory there is also the solid state physics approach. This starts from an extended surface surface model, where an array of atoms perfectly periodic in two dimensions represents both the substrate and any adsorbates. Many theoretical techniques have been developed for the extended-surface model. We can only refer the interested reader to the literature/87,88,89,90,91,92,93,94/ and remark that the relative merits of the cluster and extended-surface approaches are still very much under active debate. It is clear that certain properties, such as bonding, are very localized in character and are well represented in a cluster. On the other hand, there are properties that have a delocalized nature, such as adsorbate-adsorbate interactions and electrostatic effects, for which an extended surface model is more appropriate. 

Going beyond the single site case, the theory was recently extended such that the d molecules can have an arbitrary number of association sites [90]. In this approach the interaction between s molecules was also that of the hard sphere reference fluid. To add spherically symmetric attractions (square well, U, etc.) between s molecules, one simply needs to employ the appropriate reference system (square well, LJ, etc.). Work is currently under way to employ this association theory as a model for ion-water solvation. 

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