[lammps-users] Unstable polyethylene simulation

Hi lammps users,
I am running a lammps simulation to equilibrate polyethylene. I am using COMPASS potential. After minimization, the system was subjected to NVT at 300 K for relaxing the temperature. Then I switched to NPT. But after very few timesteps the simulation becomes unstable and the temperature, energy shoots up to a high value (non-numeric pressure, dihedral: nan errors). I have looked it up In lammps forum and found out that this could be due to bad geometry or wrong potential coefficients. I have checked my bond coefficients with the published literature. I also checked my bond stretching using OVITO. The initial geometry was created using material studio (before importing to lammps this structure was geometry optimized in material studio). I have attached my code here. Any help would be great

log.lammps (29.2 KB)

few_atoms.data (186 KB)

in.polyethylene (1.23 KB)

LAMMPS is already telling you that something is wrong! didn’t you notice this warning?

WARNING: One or more atoms are time integrated more than once

that is an indication of a serious problem.