i = createAtom ZN Zn2+ 2.0 #Create an atom i with atom name ZN, atom type Zn2+ and charge 2.0
set i element "Zn" #Set element of atom i as Zn
set i position { 0 0 0 } #Set coordinates of atom i as {0, 0, 0}
r = createResidue ZN #Create a residue r with residue name ZN
add r i #Add the atom i into residue r
ZN = createUnit ZN #Create a unit ZN with unit name ZN
add ZN r #Add the residue r into unit ZN
saveOff ZN ./atomic_ions.lib #Save information of unit ZN into atomic_ions.lib file