Hello all,
I was just wondering is it possible to create a system in LAMMPS? For example, one group contains polymer molecules and other group contains nanotubes and they can interact where the polymer molecules have a Compass forcefield and the nanotube has a different forcefield.
If it is possible how can I can achieve that?
Thank you.
Shivaji
Technically speaking, yes. But you need one more ingredient: a force field that describes the interaction between your polymer and the nanotube.
Unless there are good reasons not to do it, however, it would be preferred to use just one force field for everything. That will avoid an inconsistencies and errors resulting from combining multiple force fields with different parameterization approaches.
You would assign different atom types to the different subsystems and then using pair style hybrid.
Thank you so much Axel, I would combine the polymer , nano tube structure with another group of molecules which would use reaxff forcefield, having a system of 3 materials and the forcefields of each of the polymer, nanotube and 3rd material are not compatible with each other which led me to adopt respective forcefields.
Thanks,
Shivaji
This is a very bad idea. ReaxFF should be used for all or nothing.
You are discounting the fact, that by using a hybrid force field setup, you are introducing significant error, and those can be significant larger than the error from using a not-quite-perfect force field for part of your system.
Since your description is extremely vague, it is not possible to make any more specific suggestions outside of: whatever you choose for such a complex system, you will need to do extensive testing to validate that your choices produce meaningful results.
Thank you Axel, I’m using dreiding for PVDF polymer and tersoff for BNNT for 2 material system.
This doesn’t explain much and in the previous post, you were talking about 3 materials. Get your story straight! I very much dislike dealing with people that do not want to or do not care to provide sufficient information and context and where I have to ask for every little detail and then get inconsistent answers on top of everything.
At any rate, I have nothing to add to my previous statements. LAMMPS will not stop you to do simulations that have conceptual problems, it will execute what you tell it to do. It is up to you to prove to yourself and to whoever will review and assess your work that these are meaningful settings and that they provide a consistent answer. With pair style hybrid this is often not the case.
Apology for the confusion Axel, The system is a 3 material system with dreiding forcefield for PVDF, Tersoff for BNNT and reaxff for vanadium oxide.