The training data is gathered from the first relaxation trajectory of all 631 structures, picking up every fourth step in the ionic relaxation. The relevant configurations and local environments are then selected by BLR. The MLFFs are validated in terms of out-of-sample performance by calculating the root-mean-square force error relative to DFT results from MLFFs fitted to subsets of increasing data size (up to 600 relaxation trajectories included) against the last 31 rattled structures used in the complete training set.