In designing catalysts and reaction processes using microkinetic models, energetics of intermediates and transition states are used to predict chemical kinetics. The computed 1D-and 2D-PMFs for the surface dissociation reaction and the enthalpic and entropic contributions are shown in Figures and. The surface reaction free energy, ∆𝐺 3 = 𝐺(2N*) -𝐺(N 2 *), increases from -0.14 eV to 0.43 eV as temperature increases from 700 K to 1400 K. At low temperature, the surface dissociation reaction favors the product (2N*) while at high temperature, the equilibrium is shifted towards the reactant (N 2 *). The predicted activation energy for associative desorption, Δ𝐺 ‡ = 𝐺(TS) -𝐺(2N*), decreases from 1.94 eV at 700 K to 1.66 eV at 1400 K. The transition state has higher entropy than the 2N* state (Δ𝑆 ‡ > 0), while the activation enthalpy (Δ𝐻 ‡ ) decreases with temperature due to the greater population of higher-enthalpy dissociated states with increasing temperature. Therefore, the combined effect from enthalpic and entropic contributions causes Δ𝐺 ‡ to decrease at higher temperature. In addition to the energetics, we find differences in the critical points between FES and PES. Critical points on the PES were identified using energy minimization and transition state search methods (see the Computational Methods). A shallow local energy minimum corresponding to state M that is also predicted from energy minimization, is seen ~1 eV above the N 2 * state in averaged potential energy (or enthalpic) profiles computed from CFF-AIMD (Figures and). This intermediate precursor state has been described in previous works as an additional metastable molecularly adsorbed state along the minimum energy path. Interestingly, this minimum is absent in 1D-and 2D-PMFs (Figures and). Thus, state M is not a true metastable state within our model at the temperatures studied. These results indicate that entropic effects play a critical role in the thermal stability of intermediate precursors at finite temperatures. In nitrogen dissociation, the energetics and locations of precursors along the MFEP may affect the scattering dynamics over multiple metal surfaces, e.g., Ru(0001) and Cu(111). 9,60 Moreover, the presence of precursor states has been hypothesized to influence reaction kinetics in a variety of other surface reactions (e.g., formic acid oxidation). We also find that entropy causes a shift in the MFEP (Figure ) relative to the minimum potential energy path (Figure ). Consequently, the transition state from CFF-AIMD lies further away from the Ru surface by ~0.1 Å than what is predicted from the PES-based transition state search methods (see Computational Methods). Methods using critical points in the PES to predict free energy diagrams assume that entropy plays a minor role in determining intermediate and transition states. Our findings suggest the merit of directly identifying critical points from the FES, especially for systems with significant entropic effects.