Which kations you use to neutralize your system in GROMACS (Na+ or K+)?

GROMACS version: 2018.4
GROMACS modification: No

For anions it is simple, always CL-. For cations there is some options to choose. For example in charmm-gui membrane builder CHARMM-GUI the default option is K+, but in many GROMACS threads I saw that people use also Na+. Is there be any huge difference if you neutralize your system with a different ion or it doesn’t matter? I mostly work on membranes, so I was curious that is different ions can have an influence on for example membrane properties like area per lipid or number of hydrogen bonds or lipid etc.

It depends on the quality of the force field in terms of ion interactions with the phosphate head groups. There are specific Na+:lipid NBFIXes in CHARMM that have been validated against osmotic pressure data. I’m not sure if K+ have, but it is a global default in CHARMM-GUI for the Solution Builder, Membrane Builder, etc. Not sure why, honestly.

1 Like

@jalemkul Thank you so much.