The RMSE for the whole training set is 21.0 kcal/mol, with a coefficient of determination R 2 of 0.7. The least accurate results are for the cucurbit[n]uril complexes, for which the computed binding free energies range as negative as -68.5 kcal/mol, and the worst results are for those involving cucurbit [7]uril (CB7), with an RMSE of 41.2 kcal/mol (Table ).