  The role of solute attractive forces on hydrophobic interactions is studied
by coordinated development of theory and simulation results for Ar atoms in
water. We present a concise derivation of the local molecular field (LMF)
theory for the effects of solute attractive forces on hydrophobic interactions,
a derivation that clarifies the close relation of LMF theory to the EXP
approximation applied to this problem long ago. The simulation results show
that change from purely repulsive atomic solute interactions to include
realistic attractive interactions \emph{diminishes} the strength of hydrophobic
bonds. For the Ar-Ar rdfs considered pointwise, the numerical results for the
effects of solute attractive forces on hydrophobic interactions are of opposite
sign and larger in magnitude than predicted by LMF theory. That comparison is
discussed from the point of view of quasi-chemical theory, and it is suggested
that the first reason for this difference is the incomplete evaluation within
LMF theory of the hydration energy of the Ar pair. With a recent suggestion for
the system-size extrapolation of the required correlation function integrals,
the Ar-Ar rdfs permit evaluation of osmotic second virial coefficients $B_2$.
Those $B_2$ also show that incorporation of attractive interactions leads to
more positive (repulsive) values. With attractive interactions in play, $B_2$
can change from positive to negative values with increasing temperatures. This
is consistent with the historical work of Watanabe, \emph{et al.,} that $B_2
\approx 0$ for intermediate cases. In all cases here, $B_2$ becomes more
attractive with increasing temperature.
