Phase Transitions Affected by Natural and Forceful Molecular Interconversion

TL;DR

This paper extends classical phase separation theory to include molecular interconversion, revealing new phenomena like phase amplification and microphase separation, supported by simulations and applicable to polyamorphic liquids.

Contribution

It generalizes the Cahn-Hilliard theory to account for molecular interconversion, explaining new phase transition behaviors.

Findings

Interconversion can lead to phase amplification or microphase separation.

Simulation models confirm the theoretical predictions.

The approach applies to polyamorphic liquids and considers fluctuations near critical points.

Abstract

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.