System Not Charge Neutral with GCMC + NVT

LAMMPS LAMMPS General Discussion
1

Hi,

I’m trying to run a GCMD simulation. However, when I reach the stage of the simulation where the GCMC fix is initiated, I get an error that the system is not charge neutral:

WARNING: System is not charge neutral, net charge = -0.9999

The system is definitely charge neutral, the total charge of the input data file is ~1e-15. Regular NVT on this system works fine, and I set the charges in the molecule file (oxygen.mol) to be 0. I’m not sure exactly what’s going on. I’ve included some minimal input files for others to take a look. This is everything necessary to run a simulation.

after_anneal.data (1.1 MB)
D2020_1.8_Pt_dreiding.params (7.6 KB)
oxygen.mol (195 Bytes)
run.minimal.in (1.9 KB)
log.lammps (5.6 KB)

2

A restart file is only readable from the same computer on which it was written. Please give us a data file, which you can convert to easily with the restart2data command-line flag. Otherwise, we won’t be able to help identify the issue.

It would also help if we had a log file, so we can see exactly where the warning occured.

3

apologies, I forgot about that. I updated the post.

4

Fix gcmc should only apply to the group with which you want to exchange atoms. If you include charged atoms in your exchange, you will lose neutrality.

Your log file doesn’t show that warning, as it doesn’t show the actual run. It does have lots of other warnings though… I’m assuming it’s because you’ve made this a more minimal example?