In order to understand the dissociation reaction mechanism, we analyze the trajectories from CFF-AIMD simulations. Snapshots of the surface dissociation reaction process are shown in Figure , and the full process is shown in Movie S1. Initially, the molecular nitrogen adsorbs to the metal with its molecular axis nearly perpendicular to the surface, with an average tilt angle of 𝜙=16° (state N 2 *), as seen in the angular distribution, 𝑃(𝜙), plotted in Figure . Thermal rotation causes this on-top configuration to bend toward the surface (state A) and lie flat as 𝜙=90° (state M). As the N-N bond stretches, the adsorbate reaches a transition state, where, on average, one nitrogen atom is near an HCP hollow site, while the other approaches the closest FCC hollow site.