Toward a Specific Reaction Parameter Density Functional for H2 + Ni(111): Comparison of Theory with Molecular Beam Sticking Experiments

Abstract

Accurate barriers for rate controlling elementary surface reactions are key to understanding, controlling, and predicting the rate of overall heterogeneously catalyzed processes. The specific reaction parameter approach to density functional theory (SRP-DFT) in principle allows chemically accurate barrier heights to be obtained for molecules dissociating on metal surfaces, and such accurate barriers are now available for four H2–metal and three CH4–metal systems. Also, there is some evidence that SRP density functionals (SRP-DFs) may be transferable among systems in which the same molecule interacts with a low-index face of metals belonging to the same group. To extend the SRP database, here we take a first step to obtain an SRP-DF for H2 + Ni(111) by comparing sticking probabilities (S0) computed with the quasi-classical trajectory method with S0 measured in several molecular beam experiments, using potential energy surfaces computed with several density functionals. We find that the SRP-DF for H2 + Pt(111) is not transferable to H2 + Ni(111). On the other hand, the PBE-vdW2 functional describes the molecular beam experiments on H2 + Ni(111), which we deem to be most accurate with chemical accuracy and may therefore be considered a candidate SRP-DF for this system, of which the quality still needs to be confirmed through comparison with an experiment to which it was not fitted. However, the different molecular beam sticking measurements that we considered showed discrepancies with one another and with the theory for incidence energies > 0.2 eV, and it would be good if better defined and more accurate experiments would be done for these energies to resolve these differences.