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We make a comparison of a perturbation density functional (DF) theory and an integral equation (IE) theory with the results from Monte Carlo simulations for nonuniform fluids of hard spheres with one or two association sites. The DF used applies the weighting from Tarazona’s hard sphere density functional theory to Wertheim’s bulk first order perturbation theory. The IE theory is the associative form of the Henderson–Abraham–Barker (HAB) equation. We compare results from the theories with simulation results for density profiles and adsorption of one- and two-sited associating fluids against a hard, smooth wall over a range of temperatures and molecular densities. We also report fraction of monomers profiles for the DF theory and compare these against simulation results. For dimerizing fluids, the DF theory is more accurate very close to the wall, especially at higher densities, while the IE theory has more accurate peak heights and positions away from the wall, also especially at higher densities. Accuracy of the IE theory increases with an increasing degree of association. For two-sited hard spheres, the DF theory is more accurate than the IE theory at lower densities; at higher densities accuracies are similar to that of dimerizing hard spheres.

On the basis of a combination of the lattice gas and the linear elasticity theories, we argue that the major features of the intercalation isotherms can be well understood in terms of a coupling between the configurational and the structural transitions. Competitive effects of the internal and loading stresses are discussed. A simple model, operating with the hydrostatic parts of the stress and strain fields, is shown to be applicable to a quantitative description of experimental data on electrochemical intercalation into crystalline and layered host matrixes.

The role of a matrix response to a fluid insertion is analyzed in terms of a perturbation theory and Monte Carlo simulations applied to a hard sphere fluid in a slit of fluctuating density-dependent width. It is demonstrated that a coupling of the fluid-slit repulsion, spatial confinement, and the matrix dilatation acts as an effective fluid-fluid attraction, inducing a pseudocritical state with divergent linear compressibility and noncritical density fluctuations. An appropriate combination of the dilatation rate, fluid density, and the slit size leads to the fluid states with negative linear compressibility. It is shown that the switching from positive to negative compressibility is accompanied by an abrupt change in the packing mechanism.

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Based on a distortive lattice gas model we have investigated the intercalation of ions into a host material. It is shown that an effective potential for the ions results from the intercalation-induced distortion of the host. This interaction induces a distinct peak in the current-concentration diagram. The peak reveals a droplet formation around the distorted host domains. Theoretical results agree with experimental values for Li x TiS 2 . The ionic permselectivity effect is found to play a prominent role for the electrochemical intercalation.

Effects of weak surface fields on the density profiles and adsorption of a confined fluid near bulk criticality A comparison of density functional and integral equation theories vs Monte Carlo simulations for hard sphere associating fluids near a hard wall Density profiles and first layer adsorption isotherms of a network forming fluid near a crystalline surface are investigated using the Percus-Yevick approximation for the associative Henderson-Abraham-Barker ͑HAB͒ equation. The fluid molecule is represented as a hard sphere with four independent attractive sites. The surface is described as a hard wall with a lattice of adsorbing sites. It is shown that the association induces a new type of cooperativity related to a bridging between the adsorbing sites due to tree-like clusters adsorption. The density profiles calculated exhibit reasonably good agreement with the Monte Carlo computer simulation data. The connectivity properties of the interface are studied and an interfacial percolation threshold is predicted to exist. The mean thickness of the adsorbed layer and the connectedness wall-particle correlation functions are calculated via the connectivity analogue of the HAB equation. It is shown that the adlayer may become infinitely thick with the mean cluster size S in the bulk being finite.

An associative analogue of the Henderson-Abraham-Barker equation and its analytical solution for the Wertheim's dimerization model with a hard wall is obtained. The dependence of the adsorption on the bulk density t/and on the dimerization constant K is investigated. It is shown that the shape of the density profile allows one to draw some conclusions about the dimer orientation.