Water Evaporation: A Transition Path Sampling Study

Abstract

We use transition path sampling to study evaporation in the SPC/E model of liquid water. Based on thousands of evaporation trajectories, we characterize the members of the transition state ensemble (TSE), which exhibit a liquid-vapor interface with predominantly negative mean curvature at the site of evaporation. We also find that after evaporation is complete, the distributions of translational and angular momenta of the evaporated water are Maxwellian with a temperature equal to that of the liquid. To characterize the evaporation trajectories in their entirety, we find that it suffices to project them onto just two coordinates: the distance of the evaporating molecule to the instantaneous liquid-vapor interface, and the velocity of the water along the average interface normal. In this projected space, we find that the TSE is well-captured by a simple model of ballistic escape from a deep potential well, with no additional barrier to evaporation beyond the cohesive strength of the liquid. Equivalently, they are consistent with a near-unity probability for a water molecule impinging upon a liquid droplet to condense. These results agree with previous simulations and with some, but not all, recent experiments.

33 pages, 11 figures. Added appendix on time reversibility, fixed error in Eqs (7)-(10)

References in corpus (2)

• Extended surfaces modulate and can catalyze hydrophobic effects
• Quantifying density fluctuations in volumes of all shapes and sizes using indirect umbrella sampling

Cited by in corpus (6)

• Pathways to dewetting in hydrophobic confinement
• Spontaneous Recovery of Superhydrophobicity on Nanotextured Surfaces
• Premelting, fluctuations and coarse-graining of water-ice interfaces
• Surface Tension of Ab Initio Liquid Water at the Water-Air Interface
• Classical nucleation theory predicts the shape of the nucleus in homogeneous solidification
• Transition Path and Interface Sampling of Stochastic Schrödinger Dynamics