PACSim: A Flexible Simulation Framework for Polymer-Attenuated Coulombic Self-Assembly

TL;DR

PACSim is an open-source molecular dynamics simulation framework built on OpenMM, designed to model polymer-attenuated Coulombic self-assembly of colloids, aiding experimental and theoretical studies.

Contribution

It introduces a flexible, open-source MD simulation tool specifically for PACS, supporting diverse scenarios and methodological advancements.

Findings

PACSim enables detailed MD simulations of PACS assembly processes.

The framework supports various interaction potentials and enhanced sampling techniques.

It facilitates particle-level insights into colloidal self-assembly mechanisms.

Abstract

Polymer-Attenuated Coulombic Self-Assembly (PACS) is a flexible experimental approach for generating crystals from simple colloidal building blocks. The central components are charged spherical particles coated with a polymer brush that prevents irreversible aggregation. Whether oppositely charged colloids crystallize, and which structures they form, depends on several factors, including colloid concentration, charge, and size, as well as the salt concentration of the solution. Molecular dynamics (MD) simulations are a powerful tool for predicting the outcomes of PACS assembly experiments and also provide particle-level insight into the assembly processes. Here, we present an open-source simulation framework, PACSim, that enables MD simulation studies of assembly by PACS across a range of experimentally relevant scenarios. PACSim is built on top of OpenMM, a flexible MD simulation framework that readily supports the implementation of different interaction potentials, as well as integration with other tools such as enhanced-sampling and machine-learning frameworks. We describe the motivation for PACSim, outline its features, report methodological advancements inspired by this framework, and provide examples of its use.