Development of an Advanced Force Field for Water Using Variational Energy Decomposition Analysis

Area of Science:

• Computational chemistry
• Molecular modeling
• Force field development

Background:

• Classical force fields struggle with accurate parametrization due to piecewise modeling of intermolecular interactions.
• Many force fields neglect crucial interactions like charge transfer, relying on error cancellation, which is not always demonstrated.

Purpose of the Study:

• Introduce the many-body MB-UCB force field, designed to explicitly account for decomposed molecular interactions.
• Develop a computationally efficient and accurate force field by incorporating variational energy decomposition analysis, including charge transfer.

Main Methods:

• The MB-UCB force field was developed with design choices to minimize computational expense while maintaining accuracy.
• Parameter optimization was performed using data from single water molecules and small water clusters (up to pentamers).
• No fitting to condensed phase data was performed during optimization.

Main Results:

• High accuracy was maintained when validating against larger water clusters, liquid phase radial distribution functions, and temperature-dependent thermodynamic and transport properties.
• The MB-UCB force field demonstrated comparable performance to MB-Pol.
• MB-UCB proved to be less expensive and more transferable than previous models.

Conclusions:

• The MB-UCB force field offers a significant advancement in modeling intermolecular interactions.
• It provides an accurate and efficient alternative to existing models by explicitly including charge transfer and avoiding complex polynomial fits for short-range interactions.