openmm VS lammps

Gromacs: https://gitlab.com/gromacs/gromacs OpenMM: https://github.com/openmm/openmm Dalton: https://gitlab.com/dalton/dalton/tree/release/2020

Thanks for reporting. I haven't used CHARMMGUI myself, but I do see a similar issue that was resolved here: https://github.com/openmm/openmm/issues/3250 By chance is this relevant and/or address your problem?

Look into verlet lists or cell lists for your task, which are typically used with a discrete element method such as LAMMPS for what you seem to be describing.

Your choices are an n-body simulation (e.g., LAMMPS) with Coulomb interactions or, if your electrons are sufficiently sparse, a particle-in-cell (e.g., Starfish). Your best bets for visualization are going to be matplotlib or something more user-friendly like Visit or Paraview. Without a neutralizing background, however, your electrons are just going to repel each other, hit the walls, and disappear - there's not going to be much interesting to visualize. What are you actually trying to simulate? With more information maybe you could receive some more targeted advice.

Is this just a personal /learning project? I see "chemical simulations" and think quantum-espresso, LAMMPS, NWChem, etc. If this is a personal project, I apologize for my bluntness above.

Actually, the LAMMPS website has a similar example: Just hover over the "LAMMPS" logo in yellow and blue.

Modify the file to add what you need. In your case, modify the post_force functions in the files, since those will allow you to define the integration steps for the Vicsek model and its variations.