Whereas the simulations involve point particles moving in vacuum,
the real system involves molecules whose excluded volume
should not be ignored. One might worry that the extra pressure exerted
by the confined particles is offset by a reduction in the pressure
exerted by water molecules that would have been in the space
occupied by the particle. A kinetic view of the situation
seems to be in conflict with the predictions of the entropic
approach (in which, in the abscence of energetic terms,
the probability of a macrostate is proportional
to exp(S/k), where S is the entropy).
This is an interesting paradox of thermal physics; the same
issue arises in osmotic pressure. We believe the paradox is resolveable.
(see later page)