Swap specified ions with randomly selected solvent molecules.

randomizeions <mask> [around <mask> by <distance>] [overlap <value>] [noimage] [seed <value>]

This can be used to randomly swap the positions of solvent and single atom ions. The “overlap” specifies the minimum distance between ions, and the “around” keyword can be used to specify a solute (or set of atoms) around which the ions can get no closer than the distance specified. The optional keywords “noimage” disable imaging and “seed” update the random number seed.

An example usage is:

randomizeions @NA around :1-20 by 5.0 overlap 3.0

The above will swap Na+ ions with water getting no closer than 5.0 Å from residues 1 – 20 and no closer than 3.0 Å from any other Na+ ion.