Fig. 7.

High charge vs. transition state configurations. Distribution of the similarity between the neighborhood of the Fe atom on which $N_2$ is located and the ${\chi }_7$ state for highly charged configurations (Top) and for those in the transition state ensemble (Bottom). They are computed with a Gaussian kernel density estimation, and reweighted to reflect the equilibrium distribution (Materials and Methods). All curves are normalized such that their integral sums to 1. The snapshots below the figure are samples of the two peaks of the distribution of transition states at T = 700 K, representing configurations with high similarity (${\chi }_7$ type, Right) and low similarity (defected structures, Left). More structures are shown in SI Appendix, Fig. S17. Atoms are colored according to the charge transfer with the same color scheme as in Fig. 6.