DENSITY PROFILES FOR A DIMERIZING HARD-SPHERE FLUID NEAR AN ASSOCIATIVELY ADSORBING HARD-WALL - A MONTE-CARLO STUDY

A two-component model of dimerizing hard spheres in contact with a pen etrable hard surface is studied. The associative interaction between t he bulk fluid particles and between one of the bulk species and the ha rd surface is taken in the form of a square-well interaction. The mode l is studied by means of Monte Carlo simulations. The density profiles of the particles, the distribution of the centres of mass of the dime rs, and the number densities of dimers and particles bonded with the s urface are calculated. The effect of the strength of the associative i nteractions and the bonding distance between the bulk fluid particles and the surface is investigated. The adsorption of the adsorbed specie s is affected appreciably by the strength of the associative bond with the surface. The distance of this surface-molecule well from the surf ace affects the average orientation of the adsorbed dimers and so mimi cs orientationally specific association. Simple singlet theories are n ot very successful when there is associative adsorption or, for that m atter, when the interaction with the surface is anything other than a hard repulsion.