  A thermodynamic argument has been developed which relates the chirality of
the constituents of a mixture of enantiomers to the system excess volume, and
thereby to its Gibbs free enthalpy. A specific connection is shown between the
excess volume and the statistical mechanical partition function. The
Kihara-Steiner equations, which describe the geometry of convex hard bodies,
have been extended to include also chiral hard bodies. These results have been
incorporated into an extension of the Pavlicek-Nezbeda-Boubik equation of state
for convex, aspherical, hard-body systems. The Gibbs free enthalpy has been
calculated, both for single-component and racemic mixtures, for a wide variety
of hard-body systems of diverse volumes and degrees of asphericity,
prolateness, and chirality. The results show that a system of chiral
enantiomers can evolve to an unbalanced, scalemic mixture, which must manifest
optical activity, in many circumstances of density, particle volume,
asphericity, and degree of chirality. The real chiral molecules
fluorochloroiodomethane, CHFClI, and 4-vinylcyclohexene, C8H12, have been
investigated by Monte Carlo simulation, and observed to manifest, both,
positive excess volumes (in their racemic mixtures) which increase with
pressure, and thereby the racemic-scalemic transition to unbalanced
distributions of enantiomers. The racemic-scalemic transition, responsible for
the evolution of an optically active fluid, is shown to be one particular case
of the general, complex phase behavior characteristic of "closely-similar"
molecules (either chiral or achiral) at high pressures.
