Density functional theory for Baxter's sticky hard spheres in confinement

Area of Science:

• Statistical Mechanics
• Soft Matter Physics
• Physical Chemistry

Background:

• Fundamental Measure Theory (FMT) provides a framework for hard-sphere fluids.
• Previous applications of FMT to sticky hard-sphere fluids had limitations, particularly in confined systems.
• Scaled-particle theory and the Percus-Yevick (PY) approximation were used previously.

Purpose of the Study:

• To develop a more accurate free energy functional for sticky hard-sphere fluids.
• To resolve divergences in the strongly confined limit of these systems.
• To improve upon existing theoretical models by incorporating a new vectorial weighted density.

Main Methods:

• Combining existing FMT weighted densities with a novel vectorial weighted density.
• Regularizing divergences in the strongly confined limit.
• Comparing theoretical predictions with simulation data for bulk and confined systems.

Main Results:

• The new theory yields a free energy that is exact in the zero-dimensional limit.
• The derived direct correlation function differs from the Percus-Yevick (PY) result.
• The model accurately predicts bulk pair-correlation functions and density profiles in confinement.

Conclusions:

• The proposed method significantly enhances the accuracy of theoretical predictions for sticky hard-sphere fluids.
• The new approach overcomes limitations of previous PY-based FMT models.
• This work offers a more reliable theoretical tool for studying confined fluids.