The effect of surface relaxation on the N2 dissociation rate on stepped Ru: A transition state theory study

Abstract

The interaction between N2 and the surface results in a considerable rearrangement of the structure of the surface near the steps. The present work investigates the effect of this interaction on the rate of dissociative adsorption within the framework of harmonic transition state theory. Employing different models where selected Ru degrees of freedom are included, we show that the dominant effect of surface relaxation is a shift of the classical barrier height. Therefore, the “relaxed/N2” model, which takes relaxation of the surface into account but neglects vibrations of the surface atoms explicitly, can be used for reliable rate constant calculations. Sticking coefficients calculated employing the relaxed/N2 model based on different density-functional theory (DFT) calculations are then compared with experiment. Comparison with the experiment suggests that for the best DFT calculations the barrier height (0.49eV) is about 0.15eV too high.