I have read the piezoelectric theory in some researches, and known that the piezoelectric coefficient could be derived from calculating polarization change when the structure was deformed. And the polarization change must be determined by atom charge.

HOWEVER, I have no idea to obtain the atom charge in LAMMPS.

If you have the similar experience or any tips, could you tell me how to do that?

The linked file may be helpful on understanding the piezoelectric theory.