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Inverse density-functional theory as an interpretive tool for measuring colloid-surface interactions in dense
Mingqing Lu1, Michael A Bevan, David M Ford
1Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, USA.
The Journal of Chemical Physics
|June 25, 2005
Summary
Diffusing colloidal probe microscopy (DCPM) uses particle tracking to probe surface energy. This study develops a density-functional theory inversion method to calculate surface potentials from particle density profiles, achieving high accuracy.
Area of Science:
- Colloid and Surface Science
- Statistical Mechanics
- Optical Microscopy
Background:
- Advanced optical microscopy enables 3D tracking of colloidal particles near interfaces.
- Diffusing colloidal probe microscopy (DCPM) utilizes these particles to probe surface energetic characteristics.
- A key challenge is determining single-particle surface potentials from dense colloidal system trajectories.
Purpose of the Study:
- To develop a theoretical approach for calculating single-particle-surface potentials from experimental data in DCPM.
- To invert density-functional theory (DFT) using measured equilibrium density profiles.
- To assess the accuracy of this inversion method for dense colloidal fluids.
Main Methods:
- Developed an inversion approach based on density-functional theory (DFT).
- Calculated single-particle-surface potentials from equilibrium density profiles.
- Employed Monte Carlo simulations to generate "experimental" density profiles for model systems.
Main Results:
- The inversion procedure accurately reproduced true particle-surface potentials (within ~0.1 kT) at low to moderate densities.
- Demonstrated the method's effectiveness for hard-sphere and Lennard-Jones systems.
- Highlighted the significant impact of DFT closure approximations on accuracy.
Conclusions:
- The developed DFT inversion approach is a viable method for determining surface potentials in DCPM.
- The technique shows promise for characterizing surface energetics using colloidal particle dynamics.
- Further refinement of DFT closures is recommended for enhanced accuracy.