A fluid in contact with a wall

Abstract

The density profiles for a hard-sphere fluid in front of an ideal wall obtained either with the Percus-Yevick or the superposition approximation are compared. In an expansion of the profile in powers of the bulk density, the coefficient of the third power is better in the superposition approximation. The density at the wall is given exactly by the superposition approximation, whereas the Percus-Yevick result is too low. For the superposition approximation a calculated density profile and the excess surface density as function of the bulk density are also given.