Continuous condensation in nanogrooves.

Area of Science:

• Physical Chemistry
• Materials Science
• Thermodynamics

Background:

• Capillary condensation is crucial for understanding fluid behavior in porous materials.
• Long-range dispersion forces significantly influence phase transitions in confined geometries.
• Previous models often simplify groove geometry, limiting applicability to real systems.

Purpose of the Study:

• To investigate the mesoscopic condensation process in capillary grooves of finite dimensions.
• To analyze the influence of groove width (L) and depth (D) on meniscus behavior and phase transitions.
• To compare mesoscopic predictions with microscopic simulations using Rosenfeld's density functional theory.

Main Methods:

• Mesoscopic theoretical analysis of meniscus height (ℓ) as a function of chemical potential (μ).
• Derivation of scaling laws for meniscus growth and phase transition rounding in finite grooves.
• Validation against Rosenfeld's density functional theory (DFT) for microscopic insights.

Main Results:

• Identified crossover in meniscus growth from ℓ∼(μ_{cc}-μ)^{-1/4} to ℓ∼D-(μ-μ_{cc})^{-1/3} for finite grooves.
• Quantified the rounding of the phase transition and the chemical potential shift (δ[over ¯]μ∼D^{-3}).
• Determined meniscus height at critical chemical potential ℓ^{*}∼(D^{3}L)^{1/4} and nonmonotonic dependence of half-filling chemical potential on D.

Conclusions:

• Finite groove depth rounds the capillary condensation phase transition, shifting the filling potential.
• Mesoscopic theory accurately predicts condensation behavior, including crossover regimes and scaling laws.
• The study demonstrates the applicability of mesoscopic models and DFT for confined fluid phenomena.