where kB, h and Ga,i are Boltzmann constant, Planck constant and activation energy of i th step, respectively, and prefactor (kBT/h) is calculated to be 6.21 × 10 12 at T= 298.15 K. To estimate activation energies of thermochemical N-N bond formation steps (GM and NN mechanisms) for all transition metals, we used BEP relations based on the previous DFT results by Herron et al. .