Prediction accuracy (MUE = 1.2 1.3 1.1 kcal mol -1 ) was obtained. This is in line with current industry standards. Overall, the open source force fields performed comparably and did not show significant differences in terms of ∆∆G prediction for the results averaged over the whole set of targets and chemical series (Figures and). The obtained RMSE values from experiment are for GAFF2.1x is 1.7 2.0 1.5 , OpenFF-1.0 1.7 1.7 1.9