Bromine has the largest XDM dispersion coefficients in the test set ( C 6 = 134 a.u.). The bromine dispersion coefficients are overestimated by all three force fields. In particular, the GAFF force field grossly overestimates the strength of the bromine C 6 , with an average value of 356 a.u. The performance of GAFF for the physical properties of organobromine liquids is notably poor, suggesting that the GAFF Lennard-Jones parameters are not physically realistic. Adluri et al. showed that the GAFF model for bromomethane could be improved by reparameterizing the Lennard-Jones terms for Br.