Phase diagram and adsorption-desorption kinetics of CO on Ru(0001) from first principles

Abstract

A kinetic lattice gas model is used to study the equilibrium properties and the desorption kinetics of CO on Ru(0001). The authors compute all relevant on-site binding and interaction energies of CO molecules within density functional theory and import them in two different models. The first model allows the CO molecules to adsorb upright on top and hollow sites. The authors calculate the phase diagram, coverage isobars, and temperature programed desorption spectra. Up to a coverage of 1/3 ML, very good agreement is obtained between theory and experiment when considering top sites only. For coverages beyond 1/3 ML, hollow sites are included and disagreement between theory and experiment occurs. The second model allows adsorption on top sites only but allows them to tilt and shift from their upright positions. The authors show that this model resolves many of the deficiencies of their first one. Furthermore, the authors demonstrate that this model is more consistent with experiment since it is the only model that is able to explain the results from IR-spectroscopy experiments.

Evidence of stable high-temperature Dx-CO intermediates on the Ru(0001) surface

“…The structure of the CO overlayer is dependent on the coverage and the surface temperature. 25 On the basis of those phase diagrams, the conditions utilized in the current work (T s = 180 K) should give rise to a (…”

CO Blocking of D2 Dissociative Adsorption on Ru(0001)

“…The phase diagram of CO adsorbed on Ru(0001) has been reported on the basis of low-energy electron diffraction and theoretical studies. [23,[34][35][36] Under our experimental conditions (T S = 180 K), CO molecules are randomly adsorbed on the surface up to q CO % 0.2 ML (lattice gas). Beyond this coverage, the CO overlayer shows several complex phases, such as (…”

Deposition and crystallization studies of thin amorphous solid water films on Ru(0001) and on CO-precovered Ru(0001)

“…62,63 CO is known to adsorb in an upright geometry 64,65 on top of a Ru atom, at least up to the coverage of CO = 0.33 ML at temperatures below the desorption temperature. [66][67][68] Bonding at top sites occurs via a charge transfer from the 5 orbital of CO to the metal and a backdonation from the metal into the antibonding 2 * orbital of CO. 69,70 The continuous blueshift of CO observed up to CO = 0.33 ML has been interpreted to be due to lateral dipole coupling, 62,63 while the weakening of the bond between CO and the surface is also considered to occur and induce larger blueshift at coverages exceeding 0.33 ML. 63 With a further increase of CO dose above 0.5 L ͑ CO = ϳ 0.33 ML͒, the He intensity gradually and slightly increases up to the complete formation of the saturated structure of ͑5 ͱ 3 ϫ 5 ͱ 3͒R30°-CO/Ru͑0001͒, indicating the decrease of the corrugation of the interaction potential between He and the surface.…”