The other nitrogen atom diffuses to an empty hollow site and the N-N bond breaks. At 700 K, nearly all dissociated nitrogen atoms adsorb to HCP hollow sites (HCP-HCP), the lowest-energy 2N* state predicted from DFT calculations. However, as temperature increases to 1400 K, the nitrogen complex at the transition state dissociate into other 2N* states as well, such as HCP-FCC and FCC-FCC configurations. The fraction of HCP-FCC and FCC-FCC configurations that overlap with the 2N* state minimum increases with increasing temperature, based on calculations using a Delaunay triangulation-based adsorption site analysis (Figure ). These results suggest that there are multiple reaction pathways for N2 dissociation on Ru(0001) at high temperatures. To compute the barrier for dissociative adsorption, i.e., Δ𝐺 = 𝐺(TS) -𝐺(N2 gas ), we reference relative free energies of adsorbed states from CFF-AIMD to the gas phase, assuming ideal gas behavior for the reference state and HA for the 2N* state (see Supporting Information).