Theoretical Surface Spectroscopy of NO on the Pt(111) Surface with the DAM (Dipped Adcluster Model) and the SAC-CI (Symmetry-Adapted-Cluster Configuration-Interaction) Method

Theoretical surface spectroscopy for NO on the Pt(111) surface is carried out and combined with the experimentally known facts to elucidate the structures, absorption sites, absorption energies and K-shell binding energies of NO adsorbates on the surface. The electronic structures were studied by using the dipped adcluster model (DAM) for chemisorptions on a metal surface proposed previously and the symmetry-adapted-cluster configuration-interaction (SAC-CI) method, which is an established method for studying molecular spectroscopy. The natures of the two different adsorption species suggested experimentally have clearly been identified based on the studies on the geometries, vibrational frequencies, adsorption energies, and the N and O K-shell binding energies. The PES (potential energy surface) of NO on the metal surface was also calculated. The most stable adsorption species was on the fcc or the hcp hollow site, and the on-top one was less stable. The 2-fold bridge site did not have a minimum on the PES and therefore was only transient. The inter NO interactions at higher densities were shown to be rather weak. We examined the cluster model (CM) vs the DAM as a model of the surface adsorption on a metal surface. The CM was shown to be unable to describe the adsorption of NO on a metal surface, demonstrating the importance of the electron transfer between the NO and Pt surfaces included in the DAM. The DAM and the SAC-CI methods proved to be a useful tool for studying the nature, electronic structure, and the spectroscopic properties of the adsorbates on a metal surface.