Table : Parameters of symmetry functions. A total of 20 symmetry functions are obtained from combinations of these parameters and permutations over two atom types for 2-and 3-body descriptors. Both RMSE and maximum errors decreased more than twice. It can be seen that over the range of energies that span 5 eV (for the system of 16 H atoms), the RMSE of the refitted potential is 0.017 eV with a maximum error of 0.061 eV. This error of ∼ 1 meV per moving atom is similar to the error achieved for the CO/Pd(111) neural network potential. Errors of the underlying DFT methodology are expected to be larger. This potential is used for all calculations presented below. Since these energies correspond to a temperature of adsorbates larger than 1000 K, this potential can be used also for other types of dynamics at lower temperatures. The potential is freely available, see ref 28.