Equilibrium gas-liquid-solid contact angle from density-functional theory

TL;DR

This paper uses density-functional theory to analyze the equilibrium contact angle between gas, liquid, and solid phases, revealing conditions for phase coexistence and interface formation.

Contribution

It introduces a method to compute the equilibrium contact angle from density-functional theory considering phase coexistence and bifurcation analysis.

Findings

Bifurcation diagrams for film thickness as a function of chemical potential.

Existence of two stable film states at certain conditions.

Formation of a well-defined liquid-gas interface with a contact angle.

Abstract

We investigate the equilibrium of a fluid in contact with a solid boundary through a density-functional theory. Depending on the conditions, the fluid can be in one phase, gas or liquid, or two phases, while the wall induces an external field acting on the fluid particles. We first examine the case of a liquid film in contact with the wall. We construct bifurcation diagrams for the film thickness as a function of the chemical potential. At a specific value of the chemical potential, two equally stable films, a thin one and a thick one, can coexist. As saturation is approached, the thickness of the thick film tends to infinity. This allows the construction of a liquid-gas interface that forms a well defined contact angle with the wall.