LAUSR

Density functional theory calculations have been used to calculate activation barriers for N2 dissociation on a range of possible active sites on ruthenium nanoparticles, including step, edge and planar sites. Variations in activation barriers are rationalised through a combination of geometric and electronic effects. The lowest energy barriers are obtained using a favourable 5-fold Ru atom surface feature, although surfaces with 4-fold Ru atom features are also able to offer appreciably low barriers. The degree of undercoordination of the various sites has been quantified using generalised coordination numbers and is found to largely account for differences in activity between sites with the same geometry. Transition state energies have been converted to rate constants at typical industrial conditions using harmonic transition state theory. It is found that the most active site is the so-called B5 step site, commonly accepted to be the active site for N2 dissociation. However, several other step sites al...