General Model for Treating Short-Range Electrostatic Penetration in a Molecular Mechanics Force Field

Area of Science:

• Computational Chemistry
• Molecular Modeling
• Physical Chemistry

Background:

• Standard molecular mechanics force fields often use point charges or multipole expansions for electrostatic interactions.
• These models lack the ability to describe electron cloud penetration effects between atoms in close contact.
• Such penetration effects are significant for accurate intermolecular interaction modeling.

Purpose of the Study:

• To develop and parametrize an empirical model correcting for missing penetration terms in molecular mechanics force fields.
• To improve the accuracy of electrostatic interaction calculations in molecular simulations.

Main Methods:

• Parametrization of an empirical charge-charge function to model penetration effects.
• Creation of a database (S101×7) containing 101 molecular dimers at 7 intermolecular distances.
• Calculation of electrostatic, induction/polarization, repulsion, dispersion, and total interaction energies using the SAPT2+ method.

Main Results:

• The empirical penetration model significantly enhances the agreement between point multipole and quantum mechanical electrostatic energies.
• The model demonstrates effectiveness across various dimers and intermolecular distances.
• The parametrization requires only a limited set of parameters per chemical element.

Conclusions:

• The developed electrostatic penetration correction offers a simple yet effective method to improve molecular mechanics force fields.
• This correction addresses a critical limitation in standard force field models.
• The model is expected to become a standard feature in future molecular mechanics force fields for enhanced accuracy.