Automatic Generation of Flexible-Monomer Intermolecular Potential Energy Surfaces

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Molecular Modeling

Background:

• Accurate potential energy surfaces (PESs) are crucial for understanding molecular interactions and dynamics.
• Existing methods often require significant human intervention or assume rigid monomers, limiting their applicability.
• Developing PESs that incorporate intramonomer degrees of freedom is computationally challenging.

Purpose of the Study:

• To develop an automated method for generating nonreactive intermolecular two-body PESs that include intramonomer degrees of freedom.
• To extend the existing autoPES method by incorporating monomer flexibility.
• To provide a computationally efficient and accurate approach for PES development.

Main Methods:

• The flex-autoPES method automatically generates PESs using a sum of products of site-site functions.
• Long-range interactions are calculated from monomer properties, while the short-range part is fitted to electronic structure data.
• Symmetry-adapted perturbation theory is used to connect the long-range and short-range parts seamlessly.
• The method was tested on water dimer, ethylene glycol dimer, and ethylene glycol-water dimer systems.

Main Results:

• The flex-autoPES code successfully generated full-dimensional PESs for the tested systems.
• For the water dimer, the root-mean-square error (RMSE) was 0.03 kcal/mol, surpassing previous methods.
• RMSEs for ethylene glycol dimer and ethylene glycol-water dimer were 0.25 and 0.1 kcal/mol, respectively.
• The generated PESs are expected to be highly accurate and reliable.

Conclusions:

• The flex-autoPES method provides an automated and efficient way to generate accurate intermolecular PESs, including monomer flexibility.
• This method significantly advances the capability for molecular modeling and simulation of complex systems.
• The developed PESs offer improved accuracy for studying systems like water and ethylene glycol dimers.