GSOC 2026: Implementation of the universal pairwise potential for VdW interactions using AIM theory

[ccastilloo]

📚 Package Description and Impact

While FFprime focuses primarily on parameter derivation, an important next step is enabling the evaluation and validation of these parameters through intermolecular interaction models. In addition to electrostatic interactions, accurate modeling of molecular systems requires reliable descriptions of van der Waals (vdW) interactions, which arise from dispersion and Pauli repulsion effects.

This project aims to extend FFprime by implementing the Universal Pairwise Potential for van der Waals interactions proposed by Tkatchenko (https://pubs.acs.org/doi/10.1021/acs.jctc.3c00797), which is derived from a rigorous formalism based on Drude oscillator models. This potential provides an accurate and physically motivated description of both dispersion and Pauli repulsion contributions while maintaining computational efficiency of a force field-like potential. The parametrization of this universal potential requires atomic properties such as dispersion C_{6} and atomic polarizabilities, which can be derived from quantum-chemical calculations and partitioning schemes already implemented in FFprime.

👷 What will you do?

The student will design and implement routines in FFprime to compute intermolecular interactions using the Tkatchenko universal pairwise van der Waals potential.

• Mapping of the atomic properties (C6 and polarizability) to the Universal potential's parameters
• Functions to compute van der Waals interaction energies between atoms using the universal Tkatchenko potential

The work will also include:

• Integrating the new functionality into the FFprime architecture
• Writing unit tests to validate the implementation against analytical results and reference calculations
• Providing example workflows demonstrating how vdW interactions can be evaluated using FFprime-derived parameters

🏁 Expected Outcomes

1. New FFprime utils/potential to compute van der Waals intermolecular interactions using the Tkatchenko universal pairwise potential
2. integration with atomic polarizability and C6 coefficients derived in FFprime
3. Well-documented, tested, and maintainable code
4. Example use cases demonstrating evaluation of derived parameters through intermolecular interaction energies

Required Skills

Skill	Description
Requied Skills	Python, Scientific OOP, Linear algebra & vector calculus
Preferred Skills	Computational chemistry or molecular modeling, Familiarity with molecular simulations and force fields
Project size	Small
Difficulty	Medium

🏋️ Stretch Goal

Implement a general interaction evaluation function that allows users to compute intermolecular interactions between two molecular objects directly within FFprime. This functionality would take two NonBonded or IOData molecular objects (which contain atomic coordinates and the derived parameters) and evaluate their intermolecular interaction energy using a selected potential model.