Revisiting the hexane-water interface via molecular dynamics simulations using nonadditive alkane-water potentials

Area of Science:

• Computational Chemistry
• Molecular Dynamics
• Force Field Development

Background:

• Accurate molecular simulations require reliable force fields to represent interatomic interactions.
• Existing alkane force fields, like C27r, may not fully capture the dielectric properties crucial for systems like lipid bilayers.
• Polarizable force fields offer improved accuracy by accounting for electron cloud deformation.

Purpose of the Study:

• To develop and validate a polarizable force field for hexane using the fluctuating charge (FQ) formalism.
• To assess the performance of the FQ hexane model against the C27r model for bulk and interfacial properties.
• To evaluate the FQ model's suitability for simulating lipid bilayer interiors and interfaces with water.

Main Methods:

• Development of a polarizable force field for hexane based on the fluctuating charge (FQ) formalism and CHARMM potential.
• Molecular dynamics simulations of bulk neat hexane, hexane-water interfaces, and liquid-vapor interfaces.
• Comparison of FQ model results with the C27r alkane model and experimental data.

Main Results:

• The FQ model accurately predicts bulk density and vaporization enthalpy, outperforming C27r.
• The FQ model realistically captures hexane's dielectric properties, including optical dielectric contribution.
• Interfacial simulations show the FQ model predicts more accurate dipole potentials at liquid-vapor and hexane-water interfaces compared to C27r.

Conclusions:

• The FQ force field provides a more accurate representation of hexane's bulk and interfacial properties than the C27r model.
• The FQ model's accurate dielectric representation makes it suitable for simulating lipid bilayer interiors.
• The developed FQ force field advances the accuracy of molecular simulations for nonpolar systems.