### Physica A, 1 Oct. 1997, vol.244, (no.1-4):461-75.

### Intermolecular forces and the structure of uniform and nonuniform fluids.

Weeks, J.D.; Vollmayr, K.; Katsov, K.
### Abstract

We discuss the ramifications of Widom's idea that attractive
intermolecular forces essentially cancel in dense uniform liquids. This
idea was used directly in the WCA theory of uniform liquids, where the
structure of the liquid is approximated by that of a simpler reference
fluid with purely repulsive intermolecular forces. To take account of the
unbalanced attractive forces found in nonuniform fluids, Weeks, Selinger,
and Broughton (WSB) developed a new method where the structure is related
to that of a nonuniform reference fluid in an external field chosen to
yield a self-consistent description of correlations induced by the
repulsive forces and a mean field treatment of the attractive forces.
Using simulations, we provide a quantitative test of the accuracy of both
methods for the uniform fluid at different points in the phase diagram by
relating correlation functions in the uniform fluid to those in a
nonuniform fluid with a particle fixed at the origin. We find that at high
densities the WSB approach can correct most of the small errors in the
structure of the WCA reference fluid. At lower densities the WSB method
provides a considerable improvement over the WCA theory. A simplified
version of the WSB method is presented that is of comparable accuracy.

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