Max. Value of NaCl concentration?

GROMACS version: 2020.4
GROMACS modification: No


Does anyone know what the maximum value for “-conc” flag of genion is? and what it depends on?

I was trying to use Gromacs to simulate my experiment in which 5M NaCl solution was used (along with other buffers). But when I typed in “genion -conc 5”, Gromacs gave me an error saying “No more SOL replaceable” (or something like this).

Do you have any answers to my question, or suggestions on how to apply the experimental setting to my simulation?

gmx genion randomly replaces solvent molecules with monoatomic ions. The option -conc will add sufficient ions to reach up to the specified concentration as computed from the volume of the cell in the input [.tpr] file.
You got an error like “more water are available to be replaced by an ions.” It looks like that you system box is to small to be able to accommodate all the required ion (by replacing water molecules).
An alternative is to increase the box dimension.

Best regards