Hi @zx108s221,
I am passing by to say that this question is off topic and that I would advise you to generally avoid necroposting (see the forum guidelines for more info).
You are more likely to get relevant answer by 1. posting in the relevant category (Science Talk seems to be the most relevant, it might fit the use of the LAMMPS beginner tag in LAMMPS but this is not really a LAMMPS issue per-se), 2. make a new post detailing your issue in its title.
But this question is a methodology question and it would be wiser to dig the relevant scientific literature. The Todd and Daivis book referenced in the LAMMPS sllod manual page is an excellent starting point.