The results of the fine-tuning are shown in Table . For the SPICE database, compared to the original GAFF, our GB-FFs GAFF model significantly reduces the Root Mean Square Error (RMSE) for the energies from 5.8 kcal/mol to less than 3.0 kcal/mol and for the forces from 13.4 kcal/mol/ Å to 6.0 kcal/mol/ Å. However, for the DES370K database, the RMSE for interaction energy has increased from 1.1 kcal/mol to 1.4 kcal/mol due to the sensitivity of vdW parameters. Additionally, as stated before, GB-FFs is 3-4 orders of magnitude faster than AM1-BCC calculations using Antechamber (the command in AMBER), from 111 seconds to 0.04 seconds for 50 atoms (More details are in SI 'Computational Resources'). Furthermore, the GB-FFs charges provided by the charge transfer model closely approximate AM1-BCC charges (see Table ).