A STUDY OF ANISOTROPIC PAIR DISTRIBUTION THEORIES FOR LENNARD-JONES FLUIDS IN NARROW SLITS .1. DENSITY PROFILES AND SURFACE INTERACTIONS

Density profiles for inhomogeneous dense Lennard-Jones fluids in narrow planar slits are calculated using various integral-equation closures for the anisotropic pair distribution functions. Very good agreement with simulation studies is obtained for the Zerah-Hansen (ZH) closure and a variant of the modified hypernetted chain (MHNC) closure suggested here while the Percus-Yevick (PY), the soft-core mean spherical approximation (SMSA) and, in particular, the hypernetted chain (HNC) closures give inferior results. Various properties of the fluid as functions of the slit width are calculated in the ZH approximation, using closure parameters optimized for the bulk phase. The mean particle number per unit area virtually coincides with the values from grand canonical ensemble simulations. The net pressure between the walls, which is more difficult to calculate accurately, agrees well with the simulation result. The agreement can probably be further improved by fully optimizing the ZH closure for the inhomogeneous system. © 1990 Taylor & Francis Ltd.