Predictions for water clusters from a first-principles two- and three-body force field

Area of Science:

• Computational chemistry
• Molecular modeling
• Physical chemistry

Background:

• Accurate modeling of water interactions is crucial for understanding its properties.
• Developing efficient and accurate potentials for water clusters remains a challenge.
• Existing force fields often struggle with higher-body interactions.

Purpose of the Study:

• To develop a new rigid-monomer three-body potential for water.
• To investigate the accuracy of polarization models for many-body water interactions.
• To predict the energetics of water trimers, hexamers, and 24-mers.

Main Methods:

• Ab initio coupled-cluster calculations with augmented triple-zeta basis sets were used to compute trimer interaction energies.
• A new rigid-monomer three-body potential was fitted to these energies.
• The potential was combined with a two-body potential and a polarization model.
• Energetics of water clusters (trimer, hexamer, 24-mer) were predicted.

Main Results:

• The new rigid-monomer potential, despite its approximation, yielded predictions superior to flexible-monomer force fields.
• Simple polarization models accurately predicted four-body interactions (within a few percent).
• This contrasts with known significant errors (around 50%) in three-body interaction modeling by similar models.

Conclusions:

• The developed rigid-monomer potential offers a computationally efficient yet accurate approach for water cluster energetics.
• Simple polarization models demonstrate unexpected efficacy in capturing four-body water interactions.
• Further research into many-body interaction models for water is warranted.