Structure of a soft-sphere fluid at a soft repulsive wall: A comparison of weighted density-functional theories

Abstract

Density-functional theory is used to investigate the structure of a soft-sphere fluid at a soft wall. The fluid is modeled by an inverse sixth–power repulsive pair potential and the fluid particles interact with a flat stationary wall defined by an inverse-twelth power repulsive external potential. For comparison we examine results using three weighted density approximations (WDA), namely those due to Curtin and Ashcroft [Phys. Rev. A 32, 2909 (1985)], Denton and Ashcroft [Phys. Rev. A 39, 426 (1989)], and the partitioned WDA of Kol and Laird [Mol. Phys. 90, 951 (1997)]. The degree to which each of these approximations can accurately predict the structure of the fluid at the wall is evaluated for several densities through comparison with Monte Carlo simulation data.