Theoretical study of hydrogen dissociative adsorption on strained pseudomorphic monolayers of Cu and Pd deposited onto a Ru(0001) substrate.

We present an extensive study based on the density functional theory (DFT) of the hydrogen dissociative adsorption on strained pseudomorphic monolayers of Cu or Pd deposited onto a Ru(0001) substrate. First, the full six-dimensional potential energy surfaces (PESs) are obtained by interpolation of the DFT ab initio calculations using the corrugation reducing procedure. The accuracy of these PESs is analyzed in detail. Then, the dissociative adsorption probability has been determined by means of six-dimensional (6D) quasi-classical dynamics simulations for both normal and off-normal incidence. Although H(2) dissociation is known to be non activated on Pd(111) and strongly activated on Cu(111), we have found that it is activated on both Pd/Ru(0001) and Cu/Ru(0001). Surprisingly, the minimum activation energy for H(2) dissociation is very similar on both pseudomorphic monolayers, approximately 100 meV. In both cases, H(2) dissociation occurs after the first encounter between the molecule and the surface (direct process) and, as expected, the adsorption probabilities follow, to a good approximation, normal energy scaling.