Thermodynamics and Kinetics of Unconventional Routes to Evaporation in Liquids and Glasses

Abstract

The present dissertation advances our understanding of three unconventional routes to evaporation. All of the studies herein have been tackled with the aid of thermodynamic theory and/or atomistic molecular simulation.

We first consider the thermodynamics and kinetics of evaporation of water induced through hydrophobic confinement. In this case, the control parameter is usually the characteristic separation between the hydrophobic objects. As will be shown, the thermodynamics and kinetics of hydrophobically-induced evaporation is also extremely sensitive to the flexibility of the confining material. Such a sensitive response suggests that suggests that small changes in flexibility can induce switch-like responses between states where conformation is coupled to internal hydration, such as ion channels and receptors. We also show that the kinetics of evaporation is affected by structural features of the confined liquid film.

We then present a cavitation transition observed in the energy landscape of simple liquids and glasses. Density is the control variable. While this would typically be considered conventional, the transitions are outside the scope of equilibrium thermodynamics, as the cavitation is produced through mapping particle coordinates to the local potential energy minimum. However, we find that minimization-induced cavitation behaves analogously to a thermal phase transition. Similar behavior is observed through athermal expansion of glassy packings.

We finally consider the limits of cohesion and the origin of thermodynamic anomalies of water at negative pressure, a regime that is relatively unexplored and outside of our typical experience with the liquid state. We find that isochores without a pressure minimum can display “reentrant” behavior whereby a system that cavitates upon cooling can then rehomogenize upon further cooling. We also show that a maximum spinodal density in water results in a locus of maximum compressibility and a minimum speed of sound that are independent from any influence of a liquid-liquid critical point (LLCP). However, we demonstrate that structural signatures of a Widom line, which likely emanates from an LLCP at elevated pressure, extend to large negative pressure, but such signatures are only observed upon sampling water’s underlying potential energy landscape.