(168d) Parameterization of An Adsorbate-Adsorbate Interaction Model for Catalytic Trend Studies

The lateral interaction between atoms and molecules adsorbed on the surface of a transition metal affects both the adsorption energies of the surface species and also the transition state energies for surface reactions. A simple model for obtaining the effect of such interactions on adsorption energies is proposed, where the adsorption energy varies linearly with the coverage of species at the surface. The model is parameterized using the DFT calculated adsorption energies at different coverages for a number of atoms and molecules on the most stable facet of different transition metals.

The number of parameters in a full description of the interactions varies as N_surface × N_sp (N_sp + 1)/2, where N_sp is the number of adsorbed species and N_surface is the number of surfaces we are interested in investigating. In order to reduce the number of independent parameters we discuss 3 submodels; i) Model Rh : based on the interaction parameters of Rh{111}, ii) Model GM : the cross-interaction parameters are obtained from the parameters of the interaction between the same adsorbates, iii) Model scaled : the interaction parameters are obtained from linear scaling to the adsorption energy at low coverage. We then discuss the limitations of the proposed models, and finally for the direct decomposition of NO, we show what effect the inclusion of a description of the interactions in the kinetic model, has on the catalytic activity.