Can a liquid drop on a substrate be in equilibrium with saturated vapor?

It is well known that liquid and saturated vapor, separated by a flat interface in an unbounded space, are in equilibrium. One would similarly expect a liquid drop, sitting on a flat substrate, to be in equilibrium with the vapor surrounding it. Yet, it is not: as shown in this work, the drop evaporates. Mathematically, this conclusion is deduced using the diffuse-interface model, but it is also reformulated in terms of the maximum-entropy principle, suggesting model independence. Physically, evaporation of drops is due to the so-called Kelvin effect, which gives rise to a liquid-to-vapor mass flux if the boundary of the liquid phase is convex.

Automated summary

In equilibrium, liquid and vapor are separated, but a liquid drop on a flat substrate evaporates. This conclusion is deduced using the diffuse-interface model and reformulated in terms of the maximum-entropy principle, showing model independence. Evaporation of drops is caused by the Kelvin effect, resulting in a liquid-to-vapor mass flux when the liquid phase boundary is convex.