We performed 100 random trials with the RF model for both ∆E a and ∆E tot ads . Starting with the energy barrier, we report correlation plots (ML model vs ground truth) for the best and worst performances within the 100 trials in Figure ; Table reports the RMSE values for the training and test sets for the best and worst trials, and for the total average. The best trial provides a RMSE for the test set that is similar to that for the training set and they are both below 1 Kcal/mol, see Table ; therefore, all points are very close to the dotted line in Figure . The worst trial provides a RMSE of 3.1 Kcal/mol for the test set, even if the training set has the same RMSE as for the best trial; the plot in Figure shows most of the test-set points are further from the the ground truth than the training-set points. Nonetheless, the average over the 100 trials provides encouraging results for the fitting, as the RMSE is 1.8 Kcal/mol as shown in Table ; this error is comparable to that between the Si-12Å and Si-Min models and it is likely smaller than the expected accuracy of approximate density functionals. Furthermore, larger data sets will improve the fitting and reduce the RMSE further.