Coverage dependence of ${\mathrm{N}}_2$ dissociation at an N, O, or H precovered Ru(0001) surface investigated with density functional theory

The coverage dependence of the dissociative ${\mathrm{N}}_2$ adsorption reaction at a precovered Ru(0001) surface is investigated by means of density functional theory calculations. The energy barrier for ${\mathrm{N}}_2$ dissociation increases with the ${\mathrm{N}}_a$ or ${\mathrm{O}}_a$ precoverage and, to a lesser extent, with the ${\mathrm{H}}_a$ precoverage. The stability of the reaction products, $2{\mathrm{N}}_a,$ decreases monotonically with the precoverage. The coverage dependent $\mathrm{Ru}4d$-band center in energy, ${\varepsilon }_d,$ at the reaction site, is shown to control the energy barrier and reaction energy. The results are thereby explained in terms of a substrate mediated interaction between the dissociating ${\mathrm{N}}_2$ and the adsorbates.