Long-Range Fit: A Software Package for the Representation and Study of Long-Range Molecular Interactions

Area of Science:

• * Computational chemistry and molecular modeling.
• * Quantum chemistry and theoretical physics.

Background:

• * Accurate description of intermolecular forces is crucial for molecular system modeling.
• * Long-range molecular interactions (electrostatic, induction, dispersion) are vital in low-temperature/low-density regimes.
• * Traditional methods using perturbation theory and multipolar expansions are complex and system-dependent.

Purpose of the Study:

• * To automate the generation and fitting of long-range interaction terms for arbitrary molecules.
• * To provide a user-friendly software package for simplifying complex theoretical calculations.
• * To enable accurate modeling of molecular systems by addressing the challenges of analytical expression derivation.

Main Methods:

• * Development of the long-range-fit (LRF) software package.
• * Derivation and implementation of all interaction terms up to 15th order without approximations.
• * Utilized spherical tensor representation with symmetry adaptation to all molecular point-group symmetries.

Main Results:

• * Automated generation and fitting of long-range interaction terms for diverse molecular systems.
• * Implementation of high-order (up to 15th) interaction terms without approximations.
• * Developed a software package compatible with various close-interaction region representations.

Conclusions:

• * The long-range-fit (LRF) software package successfully automates complex calculations of intermolecular forces.
• * LRF provides a robust and efficient tool for researchers in computational chemistry and physics.
• * The generated potential energy surface enhances the accuracy and applicability of molecular modeling.