Wetting and drying at a curved substrate: long-ranged forces.

Area of Science:

• Interfacial phenomena
• Statistical mechanics
• Fluid dynamics

Background:

• Understanding fluid behavior in confined spaces is crucial for various applications.
• Interfacial properties, like surface tension, are significantly influenced by curvature and fluid interactions.

Purpose of the Study:

• To investigate the interfacial properties of a hard spherical cavity immersed in a solvent with both repulsive and attractive potentials.
• To analyze the impact of cavity size and fluid-solvent interactions on surface tension and fluid density.
• To explore wetting phenomena and their dependence on system parameters.

Main Methods:

• Utilized a coarse-grained effective Hamiltonian approach to model the system.
• Applied classical density functional theory for numerical simulations.
• Employed an exact statistical mechanical sum rule to relate fluid density and surface tension.

Main Results:

• Observed complete wetting (drying) near liquid-gas coexistence, with surface tension exhibiting a leading-order power-law nonanalyticity in curvature (R^{-2/3}).
• For states away from coexistence, surface tension expands in integer powers of curvature (R^{-1}), with additional R^{-2}lnR contributions from dispersion forces.
• Contact density shows a term in R^{-5/3} in the regime R < R(c), consistent with theoretical predictions.

Conclusions:

• The study confirms theoretical predictions regarding surface tension and contact density in spherical cavities.
• Leading-order nonanalytic contributions to surface tension are exact and robust against interface fluctuations.
• Results have implications for solvation phenomena and understanding wetting in various confined systems.