[gmx-users] problem with system neutralization

[Stefano Meliga]

Dear all,

As the on-screen output of grompp says, my system has non-zero total 
charge = -4.000

Thus, I'm trying to neutralize the system using genion with this command 
line:

genion -s 4AKEallHsol.tpr -o 4AKEallHion.gro -p 4AKEallHsol_pre.top -neutral

The problem is that the on-screen output says:

"No ions to add and no potential to calculate"
 as the system was already neutral, I guess.

I then tryied with the command line:

genion -s 4AKEallHsol.tpr -o 4AKEallHion.gro -p 4AKEallHsol_pre.top 
-neutral -np 50 -g

Ions are added to the SOL group but the total charge remains -4, as the 
log file says.

Do you know the reason?

Thanks a lot,

Stefano