Quantum size effects on chemisorption properties: CO on ultrathin Cu films from first principles

Abstract

We address, by means of ab-initio calculations, the origin of the correlation that has been observed experimentally between the chemisorption energy of CO on nanoscale Cu(001) supported films and quantum-size effects. The calculated chemisorption energy shows systematic oscillations, as a function of film thickness, with a periodicity corresponding to that of quantum-well states at Γ crossing the Fermi energy. We explain this trend based on the oscillations, with film thickness, of the decay length on the vacuum side of the quantum-well states at the Fermi energy. Contrary to previous suggestions, we find that the actual oscillations with film thickness of the density of states per atom of the film at the Fermi energy cannot account for the observed trend in the chemisorption energy.

Insight into Trimeric Formation of Nitric Oxide on Cu(111): A Density Functional Theory Study

“…We found that the E ads values oscillate with slab thickness from three to seven layers with a period of two layers, but the thickness dependence is almost negligible for slabs with more than eight layers. This oscillatory behavior is attributed to the quantum size effect of the thin Cu(111) slab used. − In the following, we report the results calculated with eight-layer slabs.…”

Water Adsorption on Na/Cu(111): State-Specific Coupling with Quantum Well States

“…The mechanism of such an enhancement, and especially its sensitive coverage dependence, has not been investigated or understood, although it was speculated that quantum well states (QWS) of the alkali metal overlayers − might be responsible for the enhanced water splitting reaction. Actually, it was found that the thin-film QWS play important roles in the thickness-dependent variations of the adsorption energy and surface reactivity for molecules and atoms on metal thin films. − Both the magnitude ,, and the decay length ,, of the electronic density of states of the film at the Fermi level have been proposed to be responsible for these quantum size effects.…”

“…Actually, it was found that the thin-film QWS play important roles in the thicknessdependent variations of the adsorption energy and surface reactivity for molecules and atoms on metal thin films. 39−47 Both the magnitude 39,41,45 and the decay length 40,43,47 of the electronic density of states of the film at the Fermi level have been proposed to be responsible for these quantum size effects.…”