[lammps-users] carbon molecular sieve

Hello everyone,

I want to produce a carbon molecular sieve (CMS) by pyrolysis PEI polymer. So, I put ten chains of PEI in a box with the amorphous cell module in Material studio with an initial density of 0.1 g/cm3.

I know I should use the ReaxFF for pyrolysis, but for preparing the initial structure, I went through two different processes:

  1. I used the Dreiding force field, annealing 300 to 700 K (NVT), compressing and decompressing from 0.1 Gpa to 1 bar at 700 K (NPT), 300 K, and 1bar (NPT) and 300 K NVT.
  2. I used the ReaxFF and the exact steps like process 1.

The final density of the structure with Dreiding equals 1.05 g/cm3 (I think it’s so dense and does not have enough porosity), but with ReaxFF, this parameter is equal to 0.45 g/cm3.

Well, I don’t know which method is correct!

Does anyone have any information or experience on preparing CMS with pyrolysis?

I want to know what to do to build the initial structure. Until then, do pyrolysis in the NVT ensemble.

I would be grateful if someone could help me.

Best regards,


The LAMMPS mailing list is not a good place to ask this kind of question since it is not really a question about LAMMPS but about how to conduct your research project.
That is a topic for a discussion with your adviser/tutor/supervisor/colleagues and for an exhaustive search of the published literature. The latter is the place where you can learn what other people have done for similar problems. A quick search of the mailing list reveals, that there have been questions in relation to pyrolysis simulations using ReaxFF with LAMMPS for more than 5 years, so there should be some publications available that describe suitable protocols and procedures. The authors of such publications would be the most suitable people to contact if you have questions beyond basic questions about setting up MD simulations or common best practices.