Physisorption fluid phase

Adsorption is brought about by the interactions between the solid and the molecules in the fluid phase. Two kinds of forces are involved, which give rise to either physical adsorption (physisorption) or chemisorption. Physisorption forces are the same as those responsible for the condensation of vapours and the deviations from ideal gas behaviour, whereas chemisorption interactions are essentially those responsible for the formation of chemical compounds. 

This work examines physical sorption ( physisorption) as the result of attraction of gaseous species into the force field (sorption potential) that exists at the heterogenic boundary at the interface between solid and fluid (vacuum) phases. Modeling of the physisorption processes involves the considerations ... 

The dynamics of any metal-liquid interface involves interactions both between and among particles in the metal and fluid. For the physisorption of water on metals, where the interaction between water molecules is comparable to the metal-water interaction, it is normally assumed that the metal-water interactions can be treated with model potentials and that a detailed quantum mechanical treatment of the interaction between the two phases is not necessary, provided an adequate model of the interaction is used. Howevei a simple quantum mechanical treatment for the metal, the jellium model, exists, and its role in the simulation of metal-water interactions also is considered below. 

As was indicated in Section I, the study of physisorption of rare gases onto simple siufaces has been the main basis for the development of theories to describe adsorption. This is especially important in the case of statistical mechanics theories, where the behavior of rare gases as simple fluids permits a large number of simplifications. It is well known that migration barriers are very small in this case [150,151], which means that the films are highly mobile, and can thus be adequately represented by statistical mechanics models describing 2D fluids. In addition, theoretical calculations [33] are facilitated by the fact that the solid is composed of one kind of atom. Finally, there is added interest in the great variety of adsorbed phases that may be present. 

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