Confinement of Ar between two identical parallel semi-infinite walls

Area of Science:

• Physical Chemistry
• Materials Science
• Computational Physics

Background:

• Understanding fluid behavior in confined geometries is crucial for materials science and nanotechnology.
• Previous studies often simplified substrate-fluid interactions, limiting realistic modeling.
• Alkali metals, alkaline-earth metals, and CO2 present diverse substrate-fluid interaction potentials.

Purpose of the Study:

• To investigate the confinement effects of Argon (Ar) gas in planar slits with various wall materials.
• To explore the phenomenon of spontaneous symmetry breaking (SSB) in confined systems.
• To analyze the influence of substrate-fluid interaction strength, temperature, and slit width on Ar density profiles.

Main Methods:

• Density Functional Theory (DFT) was employed for theoretical investigation.
• Realistic effective pair potentials for Ar-Ar interactions were utilized.
• Ab initio potentials described Ar adsorption on alkali metal, Mg, and CO2 walls.

Main Results:

• For low Ar coverage, slits fill symmetrically with vapor films at each wall.
• Alkali metal substrates exhibit spontaneous symmetry breaking (SSB) at specific densities and temperatures, characterized by asymmetric Ar density profiles.
• SSB diminishes with increasing temperature, disappearing at a critical temperature coinciding with critical prewetting temperature (T(cpw)). Mg and CO2 substrates did not show SSB.

Conclusions:

• The study demonstrates that substrate properties significantly influence confined fluid behavior, including the emergence of SSB.
• Spontaneous symmetry breaking is a temperature-dependent phenomenon in Ar confined by alkali metals.
• The findings provide insights into phase transitions and adsorption phenomena in nanoconfined systems.