Revised charge equilibration potential for liquid alkanes.

Area of Science:

• Computational Chemistry
• Molecular Modeling
• Physical Chemistry

Background:

• Existing liquid alkane force fields have limitations in accurately describing dihedral potentials, electrostatic, and Lennard-Jones parameters.
• Nonadditive electrostatic effects due to local polarization require advanced modeling formalisms.

Purpose of the Study:

• To present a revised liquid alkane force field incorporating charge equilibration for nonadditive electrostatics.
• To address and rectify deficiencies in dihedral, electrostatic, and Lennard-Jones parameters of a previous model.
• To enhance the accuracy of molecular simulations for linear alkanes.

Main Methods:

• Refinement of alkane backbone torsion potentials using high-level ab initio calculations.
• Adjustment of electrostatic and Lennard-Jones parameters to match experimental data for hexane (polarizability, density, enthalpy of vaporization).
• Calculation of bulk liquid properties and free energies of hydration for various linear alkanes.

Main Results:

• The revised force field demonstrates significantly improved accuracy in predicting bulk liquid properties compared to the original model.
• Accurate reproduction of experimental polarizability, liquid density, and vaporization enthalpy for hexane.
• Successful calculation of densities, enthalpies of vaporization, diffusion constants, compressibilities, heat capacities, and NMR relaxation times.

Conclusions:

• The revised liquid alkane force field provides a superior description of molecular and bulk properties.
• This model serves as a foundation for developing polarizable force fields for lipids and membrane proteins within the CHARMM framework.
• The improved force field enhances the predictive power of molecular simulations for alkane systems.