The results are reported in Figure and Figure . As shown in Figure , without systemspecific optimization, the original GAFF model generates significant outliers in density, and the predicted conductivities show essentially no correlation with experimental results. This performance clearly illustrates the deficiency of universal FF in electrolyte screening, and MD simulations using such a FF can be seriously misleading. For comparison, the charge-scaled model performs much more robustly in conductivity predictions when the right scaling factor is used. However, since charge parameterization is strongly coupled with LJ parameters, adjusting charges alone significantly deteriorates the model performance in densities (Figure ) and evaporation enthalpies (Table ). In Figure , we show the trends of density and conductivity errors during the density optimization cycles starting from the charge-scaled models. For all charge scaling factors, by optimizing density, the electrical conductivity error is also reduced. This shows how the learned parameters can be transferred in the predictions of different properties. We find that the inclusion of EG evaporation enthalpy in the fitting target worsens the accuracy of conductivity. This shows the balance between dynamic and thermodynamic properties, which is an inherent limitation originating from the inaccurate function form used in the classical FF. Nevertheless, compared to the charge-scaled model, the final optimized model still shows better performance in electrical conductivity, regardless of the scaling factor. In addition, the predictions of the density and evaporation enthalpy are also significantly more accurate (see Figure and Table ). We also note that the improvement achieved in the EG evaporation enthalpy is also observed for GI, which was not included in the fitting target, proving the excellent chemical transferability of the optimized model (see Table ). Therefore, we conclude that the automatically optimized FF reaches a much better performance compared to both initial GAFF and charge-scaled GAFF (regardless of the value of the scaling factor) and thus will be used in all subsequent studies.