A Simple Electron-Density Based Force Field Model for High-Energy Interactions between Atoms and Molecules.

Area of Science:

• Computational Chemistry
• Materials Science
• Statistical Mechanics

Background:

• Standard force fields are inadequate for high-energy simulations (e.g., hot gases, plasmas) due to limitations in their repulsive terms.
• Accurate modeling of repulsive interactions is crucial for simulating extreme conditions.

Purpose of the Study:

• Introduce a novel force field model for high-energy simulations.
• Improve the accuracy of repulsive potential energy calculations.

Main Methods:

• Developed a pair approximation model based on electronic densities of noninteracting atoms/molecules.
• Incorporated an exchange-correlation term calibrated using CCSD(T)/cc-pVTZ *ab initio* calculations.
• Compared the model's repulsive potential energy hypersurfaces with existing force fields for small molecule dimers.

Main Results:

• The proposed force field model accurately captures the repulsive parts of potential energy hypersurfaces.
• The derived exchange-correlation function improves upon standard models for high-energy regimes.
• Validation performed on dimers of small molecules demonstrates improved performance.

Conclusions:

• The new force field model offers a more reliable approach for high-energy simulations.
• Accurate representation of repulsive forces is essential for modeling extreme states of matter.
• This work provides a foundation for developing better force fields for diverse simulation conditions.