Of the intermediate-cost group M 4,2 yields the lowest RMSE of 0.12 eV for the training set, however its performance deteriorates significantly for the validation set with an RMSE of 0.18 eV without terphenyl (0.27 eV with terphenyl), indicating over-fitting. The next model M 2,3 has a more robust performance with RMSEs of 0.12 eV for the training set and 0.13 eV for the validation set without terphenyl (0.22 eV with terphenyl).