# An automated calculation pipeline for differential pair interaction energies with molecular force fields using the Tinker Molecular Modeling Package

## TL;DR

This paper introduces an automated pipeline using Tinker to calculate interaction energies between molecular pairs, enabling efficient generation of repulsion parameters for simulations.

## Contribution

The paper introduces the first open computational pipeline for calculating differential pair interaction energies using molecular force fields.

## Key findings

- The pipeline successfully approximates global minimum energy structures and calculates differential pair interaction energies.
- Flory–Huggins parameters and DPD repulsions were derived for a surfactant-water mixture using multiple force fields.
- The approach was validated using DFT calculations and DPD simulations.

## Abstract

An automated pipeline for comprehensive calculation of intermolecular interaction energies based on molecular force-fields using the Tinker molecular modelling package is presented. Starting with non-optimized chemically intuitive monomer structures, the pipeline allows the approximation of global minimum energy monomers and dimers, configuration sampling for various monomer–monomer distances, estimation of coordination numbers by molecular dynamics simulations, and the evaluation of differential pair interaction energies. The latter are used to derive Flory–Huggins parameters and isotropic particle–particle repulsions for Dissipative Particle Dynamics (DPD). The computational results for force fields MM3, MMFF94, OPLS-AA and AMOEBA09 are analyzed with Density Functional Theory (DFT) calculations and DPD simulations for a mixture of the non-ionic polyoxyethylene alkyl ether surfactant C10E4 with water to demonstrate the usefulness of the approach.

Scientific Contribution

To our knowledge, there is currently no open computational pipeline for differential pair interaction energies at all. This work aims to contribute an (at least academically available, open) approach based on molecular force fields that provides a robust and efficient computational scheme for their automated calculation for small to medium-sized (organic) molecular dimers. The usefulness of the proposed new calculation scheme is demonstrated for the generation of mesoscopic particles with their mutual repulsive interactions.