Molecular Dynamics simulation of evaporation processes of fluid bridges confined in slit-like pore

TL;DR

This paper uses molecular dynamics simulations to study the equilibrium and kinetics of fluid bridges confined in slit-like pores, focusing on evaporation, wetting properties, and diffusion processes.

Contribution

It provides new insights into the equilibrium configurations and diffusion dynamics of confined fluid bridges with varying wetting conditions.

Findings

Diffusion constants vary significantly between confined and bulk phases.

Equilibrium configurations depend on wall-fluid interaction strength.

Kinetics of evaporation and filling are characterized by diffusion processes.

Abstract

A simple fluid, described by point-like particles interacting via the Lennard-Jones potential, is considered under confinement in a slit geometry between two walls at distance Lz apart for densities inside the vapor-liquid coexistence curve. Equilibrium then requires the coexistence of a liquid "bridge" between the two walls, and vapor in the remaining pore volume. We study this equilibrium for several choices of the wall-fluid interaction (corresponding to the full range from complete wetting to complete drying, for a macroscopically thick film), and consider also the kinetics of state changes in such a system. In particular, we study how this equilibrium is established by diffusion processes, when a liquid is inserted into an initially empty capillary (partial or complete evaporation into vacuum), or when the volume available for the vapor phase increases. We compare the diffusion constants describing the rates of these processes in such inhomogeneous systems to the diffusion constants in the corresponding bulk liquid and vapor phases.