Simple Parameter-Free Bridge Functionals for Molecular Density Functional Theory. Application to Hydrophobic...

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Soft Matter Physics

Background:

• Computer simulations are crucial for understanding hydrophobic solvation and interactions.
• Existing liquid-state theories lack the completeness and accuracy of simulations.

Purpose of the Study:

• Introduce a classical, molecular density functional theory for hydrophobic solvation.
• Improve the accuracy of existing theories, particularly concerning cavitation free energies.

Main Methods:

• Developed a molecular density functional theory approach.
• Incorporated two simple, angular-independent bridge functionals to correct approximations.
• Utilized water bulk properties (pressure, compressibility, surface tension) for parameter-free calibration.

Main Results:

• The corrected theory accurately reproduces solvation free energies for hydrophobes of various sizes (microscopic to nanoscale).
• Achieved high accuracy (within 0.25 kBT) compared to Monte Carlo simulations for over 600 model hydrophobic molecules.
• A weighted density approximation proved effective, unlike a hard-sphere bridge functional.

Conclusions:

• The developed theory provides a robust and accurate method for predicting hydrophobic solvation free energies.
• This work serves as a foundation for functionals describing both hydrophobic and hydrophilic solvation.
• Enables the study of non-idealized hydrophobic interactions with improved accuracy.