We study the structure around a dilute Lennard-Jones (LJ) solute in a super
critical LJ fluid using integral equation theories and Monte Carlo simulati
on. We show that the Percus-Yevick approximation can be seriously in error
in the near-critical region. The solute's coordination number as a function
of the solvent density can be nearly linear, or quite non-linear, dependin
g on the solute-solvent interaction. These results are rationalized as a cr
ossover from a low-density energy-dominated regime to a high-density entrop
y-(packing-) dominated regime, and are discussed within the context of the
local density enhancement concept. (C) 2000 Elsevier Science B.V. All right
s reserved.