Which is the maximum number of atoms, which can Lammps support? I tried to use systems(polymer systems) including close to 1,7 millions atoms and my simulations stopped. I used a large cut off too for the simulations.
For bonded systems the max is 2 billion. For systems w/out bonds,
it's effectively unlimited. So you have another problem. If "stopped"
means hung, then it may just be you are doing some very expensive
computation, like a long cutoff implies.