Reactive scattering ofH2from metal surfaces under fast-grazing-incidence conditions

Abstract

We have studied the interaction of molecular hydrogen with metal surfaces under fast-grazing-incidence conditions, by means of classical dynamics calculations based on density functional theory six-dimensional potential energy surfaces. We have performed calculations on two activated systems, ${\mathrm{H}}_{2}$/NiAl(110) and ${\mathrm{H}}_{2}$/Cu(111), and on two nonactivated systems, ${\mathrm{H}}_{2}$/Pd(111) and ${\mathrm{H}}_{2}$/Pd(110). We show that for rather open surfaces the computed $1\ensuremath{-}R$ probabilities (where $R$ represents the reflectivity) as a function of the normal collision energy at grazing incidence (along low-Miller-index directions) mimic reasonably well the dissociative adsorption probabilities obtained at normal incidence and thermal energies from the dissociation threshold up to the saturation limit. Our results indicate that fast grazing incidence experiments could be used as complement to traditional sticking experiments at thermal energies to determine dissociative adsorption saturation limits, which are usually unreachable due to limitations in traditional molecular beam experiments