System has non-zero total charge

GROMACS version:
GROMACS modification: Yes/No
Dear Gmx Users,
I am dealing with a 380k atoms system whose net charge is not “strictly” zero.
During the grompp generation, indeed, gromacs detects a net charge equal to -0.018.
I do believe this is a numerical problem, do you think it is correct to use the option maxwarn -1 in order to ignore the warning and go ahed running the simulation?

Thanks in advance


It looks a little too large to be a rounding error. You can check the topology by looking at the right-hand comment column of the atom listing (in the topology), which lists the cumulative charge. This should be an integer after every residue (and/or charge group where applicable). This will assist in finding the residue where things start departing from integer values. Also check the terminal capping groups that have been used.

Best regards