Completely Multipolar Model as a General Framework for Many-Body Interactions as Illustrated for Water

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Materials Science

Background:

• Accurate modeling of intermolecular interactions is crucial for understanding chemical systems.
• Existing force fields often struggle with describing complex many-body effects and short-range interactions.
• Energy Decomposition Analysis (EDA) provides valuable insights into the nature of these interactions.

Purpose of the Study:

• To introduce a general and robust framework for many-body force fields, the Completely Multipolar Model (CMM).
• To establish a common functional form for all terms in an energy decomposition analysis of intermolecular interactions.
• To ensure accurate description of both long- and short-range interactions, avoiding short-range catastrophes.

Main Methods:

• Developed the Completely Multipolar Model (CMM) using multipolar electrical moments modulated by exponential decay of electron density.
• Formulated well-behaved damped tensors for EDA terms: dispersion, exchange polarization, Pauli repulsion, polarization, and charge transfer.
• Incorporated a one-body potential with an electric field-dependent correction to the Morse potential for intramolecular polarization.

Main Results:

• CMM successfully describes separable EDA terms with short-ranged anisotropy and intramolecular charge fluctuations.
• The model naturally incorporates many-body charge transfer by coupling into polarization equations.
• CMM reproduces key monomer properties, including dipole moment and polarizability, and shows excellent agreement with water cluster data.

Conclusions:

• The Completely Multipolar Model (CMM) provides a general and accurate framework for many-body force fields.
• CMM offers a unified approach to modeling intermolecular interactions, improving upon existing methods.
• The model's ability to reproduce monomer properties and cluster data validates its effectiveness.