Toward a Physically Motivated Force Field: Hydrogen Bond Directionality from a Symmetry-Adapted Perturbation Theory...

Area of Science:

• Computational Chemistry
• Molecular Modeling
• Quantum Chemistry

Background:

• Popular force fields often use restrictive functional forms, limiting accurate, physics-based parametrization.
• Intermolecular interactions are crucial for understanding molecular behavior and chemical processes.

Purpose of the Study:

• To propose modifications to existing force fields for improved accuracy.
• To develop a physics-based approach for parametrizing intermolecular interactions.
• To analyze the contributions to binding energy and hydrogen bond directionality.

Main Methods:

• Utilized symmetry-adapted intermolecular perturbation theory (SAPT).
• Separated intermolecular interaction energy into electrostatics, exchange-repulsion, dispersion, and induction.
• Approximated electrostatic energy using short-range penetration and long-range distributed atomic multipoles.
• Employed a distributed induced damped point dipole model for induction energy.
• Fitted dispersion energy to an analytical function and approximated exchange-repulsion via monomer charge density overlap.

Main Results:

• The proposed method allows for accurate and physics-based parametrization of force fields.
• Analysis of the water dimer reveals that polarization contributions (induction and dispersion) drive its geometrical preference.
• The four-component energy decomposition provides deeper insight into hydrogen bond directionality.

Conclusions:

• The developed approach offers a more robust and accurate method for molecular modeling.
• Understanding the individual contributions to intermolecular forces is key to improving predictive power.
• This framework has the potential for broader applications in computational chemistry.