[lammps-users] How to define virtual atoms in the lammps?

Dear LAMMPS users,

I need to build a molecule having a virtual atoms for the lone pair on the specific atoms. I made lammps data file and ran simulation. But it crashes at the beginning of the simulation. The error message says “Cannot compute PPPM”. I think this is because of lone pair atoms since they are attached really closely to the bonded atoms. To figure out the problems, I shifted virtual atoms, but still crashes. I visualized with vmd. As I expected, the virtual atom flies away. Can anyone help me to figure the problem out?

With my regards

there is not enough information here to provide any specific advice. also, the (partial) error message you quote can have multiple reasons.

what I can say in general is that LAMMPS doesn’t support virtual sites except if you use fix rigid or fix rigid/small and treat the entire group of atoms including the virtual site as a rigid object.
you still need to assign a mass, but that may be tiny.

for people to give advice, you need to create a minimal example (with just a few atoms/molecules) that demonstrates the issue quickly, so people can have a close look and run it themselves to assess what the problems are.
there rarely is just that one specific command that needs to be added or changed to resolve issues.