Title: Adsorption of hard spheres: structure and effective density according to the potential distribution theorem
Author(s):

	L.L. Lee (Department of Chemical \& Materials Engineering, California State University, Pomona, California, USA ) ,
	G. Pellicane (School of Physics, University of Kwazulu-Natal, Private Bag X01 Scottsville, 3209 Pietermaritzburg, South Africa )

We propose a new type of effective densities via the potential distribution theorem. These densities are for the sake of enabling the mapping of the free energy of a uniform fluid onto that of a nonuniform fluid. The potential distribution theorem gives the work required to insert a test particle into the bath molecules under the action of the external (wall) potential. This insertion work W_ins can be obtained from Monte Carlo (MC) simulation (e.g. from Widom's test particle technique) or from an analytical theory. The pseudo-densities are constructed thusly so that when their values are substituted into a uniform-fluid equation of state (e.g. the Carnahan-Starling equation for the hard-sphere chemical potentials), the MC nonuniform insertion work is reproduced. We characterize the pseudo-density behavior for the hard spheres/hard wall system at moderate to high densities (from ρ*= 0.5745 to 0.9135). We adopt the MC data of Groot et al. for this purpose. The pseudo-densities show oscillatory behavior out of phase (opposite) to that of the singlet densities. We also construct a new closure-based density functional theory (the star-function based density functional theory) that can give accurate description of the MC density profiles and insertion works. A viable theory is established for several cases in hard sphere adsorption.

Key words: potential distribution theorem, hard spheres, adsorption, effective density, structure, integral equation, closure
PACS: 68.43.De

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