Fig. 2: Exploration stage: iterative discovery of reaction paths through flooding simulations and GP-based MD.

We report a schematic presentation for the case of N₂ dissociation. a The reactant free energy landscape constructed at the end of the preliminary phase, highlighting the metastable minima (gas phase and two adsorption states). Arrows indicate that the reaction paths toward the product state are unknown a priori. Several iterations are then initiated from the reactant basin. The time evolution of the distance between N atoms d_N,N (b) and the GP maximum uncertainty on the local environments (c) are shown for a specific iteration. Every time the uncertainty of the GP exceeds the threshold of 0.1 (red dotted line), energy and forces are recomputed at the DFT level (red dots), and the GP is updated. Panel d shows all iterations in the 2D space defined by d_N,N and the coordination number between N and surface atoms C_N,Fe∣Co, with the trajectory shown in b, c highlighted. Above the top axis, we report the distribution of points where DFT calculations were performed, projected along d_N,N. Snapshots and graphs were made with Ovito⁸⁶ and Matplotlib⁸⁷, respectively.