  If a binary liquid mixture, composed of two alternative species with equal
amounts, is quenched from a high temperature to a low temperature, below the
critical point of demixing, then the mixture will phase separate through a
process known as spinodal decomposition. However, if the two alternative
species are allowed to interconvert, either naturally (e.g. the equilibrium
interconversion of enantiomers) or forcefully (e.g. via an external source of
energy or matter), then the process of phase separation may drastically change.
In this case, depending on the nature of interconversion, two phenomena could
be observed: either phase amplification, the growth of one phase at the expense
of another stable phase, or microphase separation, the formation of nongrowing
(steady-state) microphase domains. In this work, we generalize the
Cahn-Hilliard theory of spinodal decomposition to include molecular
interconversion of species and describe the physical properties of systems
undergoing either phase amplification or microphase separation. We apply the
developed theory to describe the simulation results of three atomistic models
which demonstrate phase amplification and/or microphase separation. We also
discuss the application of our approach to phase transitions in polyamorphic
liquids. Lastly, we describe the effects of fluctuations of the order parameter
in the critical region on phase amplification and microphase separation.
