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Electronic structure of CO adsorbed on a Cu(111) surface analyzed with molecular cluster models

1982; American Physical Society; Volume: 26; Issue: 8 Linguagem: Inglês

10.1103/physrevb.26.4073

1095-3795

Jean‐François Paul, Arne Rosén,

nanoparticles nucleation surface interactions

Using the self-consistent Hartree-Fock-Slater model we have calculated the electronic structure for various ${\mathrm{Cu}}_{x}{(\mathrm{CO})}_{y}$ clusters symbolizing not only CO bound to "on-top" and "bridge" sites but also some lateral CO-CO interaction on a Cu(111) surface. By comparison with experimental photoemission data we are able to reproduce the observed energies of the occupied CO $4\ensuremath{\sigma}$, $1\ensuremath{\pi}$, and $5\ensuremath{\sigma}$ orbitals as well as the partly occupied $2\ensuremath{\pi}$ orbital. In our model we assume CO to be adsorbed on "top" sites for coverages less than $\ensuremath{\bigominus}=0.33$ [$(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$] and on both top and bridge sites for $\ensuremath{\bigominus}>0.33$. The experimentally observed peak of intensity at the Fermi edge which increases with coverage above 0.33 is in our model explained by the occupation of CO orbitals of the ${b}_{1}$ and ${b}_{2}$ symmetry types, i.e., "$\ensuremath{\pi}$" orbitals, degenerate for top positions (${C}_{3v}$), split by the change to bridge positions (${C}_{2v}$). Our results further indicate that the broadened $5\ensuremath{\sigma}\ensuremath{-}1\ensuremath{\pi}$ intensity peak at high coverages is a result of CO bound to top and bridge sites.