Comparison of overlap-based models for approximating the exchange-repulsion energy

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Modeling

Background:

• Accurate calculation of exchange-repulsion energy is crucial for molecular simulations.
• Classical potential functions offer a computationally efficient alternative to ab initio methods.
• Existing approximations for exchange-repulsion energy require careful evaluation.

Purpose of the Study:

• To investigate and compare different classical potential functions for approximating exchange-repulsion energy.
• To assess the accuracy of orbital overlap and electron-density overlap methods.
• To evaluate the performance of the effective fragment potential (EFP) model.

Main Methods:

• Fitting various classical potential expressions to exact exchange-repulsion energies of molecular dimers.
• Utilizing orbital overlap and electron-density overlap as key components in the potential functions.
• Comparing the performance of these approximations against the parameter-free EFP model.

Main Results:

• Exchange-repulsion energy shows near proportionality to both orbital and density overlap.
• Distance-dependent corrections are essential for accurate approximations in both overlap methods.
• Orbital overlap approximations are superior to density overlap when few parameters are used.

Conclusions:

• Orbital overlap approximations with a few parameters provide a balance of accuracy and simplicity.
• The EFP model performs well but shows limitations with delocalized pi systems.
• Classical potential functions based on orbital overlap are promising for efficient molecular modeling.