Energy transfer in elementary reactive processes at metal surfaces

Abstract

Advances in the description of elementary reactive processes at surfaces are largely triggered by the quest for systems and conditions under which reactivity can be controlled, enhanced or inhibited. Here we review recent theoretical work on the dynamics of physical and chemical processes taking place when hydrogen and nitrogen atoms and molecules interact with clean and decorated metal surfaces. The theoretical framework relies on multidimensional potential energy surfaces built from ab-initio calculations and classical dynamics. Fully ab-initio molecular dynamics are used in some cases as well. We pay special attention to the energy exchange with the surface, included through the excitation of electron-hole pairs and phonons. We actually evaluate the role of these two energy dissipation channels in the scattering and adsorption of N2 on W(110) and N on Ag(111), as well as on the relaxation of H hot atoms on Pd(100). In the case of N atoms incident on N-covered Ag(111), we show that the Eley-Rideal recombination process between gas-phase N atoms and N adsorbates is a highly efficient mechanism for N2 formation. We discuss the importance of the particular crystal face of the surface on the adsorption process, taking as example the interaction of N2 molecules with W and Fe surfaces. We demonstrate that surface strain can be a useful tool to tune reactivity. We conclude that relatively small variations in interaction energies can lead to drastic changes in the dynamics and thus to significant modifications in the final output of the scattering process.