LAMMPS active matter

Dear LAMMPS users, developers, and researchers,

I was trying to perform an active matter simulation on LAMMPS using fix_langevin. I have added self-propel force and got the required Mean Square Displacement vs. time graph for active matter but didn’t get cluster formation. Does anyone know how to perform active matter simulation on LAMMPS and tell me what I am missing?

Best regards

Your description is far too vague so that anybody can make any meaningful suggestions.