Here, however, our set is relatively small, so it is important to not place too much confidence in any analysis of systematic errors. Still, such analysis can suggest likely targets needed for follow up studies to confirm potential problems, and some trends seem clear. Here, based on our analysis of errors in activity coefficients broken down by the functional group observed in the solute, we found that sulfoxide had the largest absolute value of the average error of the set (Figure ). In fact, the only sulfoxide present in the set was dimethylsulfoxide (DMSO), and all IDACs involving DMSO were for this molecule in different solvents (DMSO was never present as a solvent in the simulations). The average error of +1.4 ± 0.2 kcal/mol suggests a systematic error in the GAFF description of DMSO (Fig. ).