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.

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