Chlorine has a large average XDM dispersion coefficient ( C 6 = 70.8 a.u.), but also has a relatively small standard deviation (σ = 1.0 a.u.). The force-field dispersion coefficients for chlorine are much larger than the XDM values. The GAFF and OPLS force field share Lennard-Jones parameters for chlorine, so their C 6 coefficients are also the same (C 6 = 135 a.u.), while the CGenFF force field assigns even larger values ( C 6,Cl = 154 a.u.).