Equation of state for confined fluids

Area of Science:

• Thermodynamics
• Physical Chemistry
• Statistical Mechanics

Background:

• Bulk fluids are described by equations of state, but confined fluids present challenges due to surface interactions.
• Predicting thermodynamic properties of confined fluids requires accounting for surface effects, which existing models struggle with.

Purpose of the Study:

• To develop a consistent thermodynamic framework for an equation of state applicable to pure, confined fluids.
• To accurately incorporate surface contributions into the equation of state for confined systems.

Main Methods:

• Decomposing the system into bulk and surface phases in equilibrium.
• Utilizing Gibbs' framework for surface excess properties to integrate surface contributions.
• Applying the equation of state to a Lennard-Jones fluid confined by a spherical surface.

Main Results:

• The proposed equation of state accurately predicts pressure and internal energy compared to molecular dynamics simulations.
• Properties of highly curved surfaces can be predicted from planar surface data by selecting an appropriate dividing surface.
• The framework is independent of ensemble and applicable to diverse system geometries and interactions.

Conclusions:

• The developed thermodynamic framework provides a robust method for predicting properties of confined fluids.
• This approach offers a pathway for accurate thermodynamic modeling in complex systems like porous media.
• The framework's versatility makes it suitable for a wide range of confinement scenarios.