[gmx-users] Position Restrained of ions

[Steven Neumann]

Dear Gmx Users,

i wish I could restrain some ions in my system (NA). I tried to include it
in ions.itp:

[ moleculetype ]
; molname    nrexcl
NA        1

#ifdef POSRES_NA
[ position_restraints ]
; atom  type      fx      fy      fz
     1     1  1000  1000  1000
#endif

But it does not work. Would you advise please?

Steven