I am trying to simulate Ti–N (mainly Ti₂N) using the COMB3 potential. I already have the potential file and input script, but I am facing confusion regarding the LAMMPS data file format and charge assignment.
For standard potentials that I previously used (e.g., MEAM, airebo ), I typically use a default data file generated from Atomsk/OVITO with:
Atoms # atomic
id type x y z
However, for COMB3 / ReaxFF charged optimized, I understand that the format requires charges:
Atoms # charge
id type q x y z
Since my structure (generated via Atomsk) did not include charges, I manually modified the data file by adding a q column and setting all charges to 0.0, which might not be correct and I couldn’t really find any useful sources in this regard. or should I have used the set command to set the charges.
I also observe instability during NPT equilibration (atoms distort/break even before deformation), so I am clueless whether this is due to the data file format that I am using or the input script (which is less likely since I used the same script with different potential and it worked fine). I would just like to know how to deal with this issue. Thankyou.