TY - JOUR
T1 - Molecular cluster calculations for the interpretation of CO chemisorption on a Ni(100) surface
AU - Rosén, A.
AU - Baerends, E. J.
AU - Ellis, D. E.
N1 - Funding Information:
One of the authors (A.R.) gratefully acknowledgest he support by Professor I. Lindgren and for discussionsa nd commentso n the manuscriptb y Dr. S. Andersson. Financial support from the Swedish Natural Science ResearchC ouncil is gratefully recognized.T he calculations were performed at Gothenburg University Computing Centre and at Gesellschaft fur Schwe~onenfors~hung(W I) Darmstadt. Thanks should be given to ProfessorB . Fricke for arrangingm y visits at GSI.
PY - 1979/3/2
Y1 - 1979/3/2
N2 - Self-consistent Hartree-Fock-Slater molecular cluster calculations for the chemisorption of carbon monoxide on a Ni(100) surface are presented. In earlier calculations of this type the CO molecule has been assumed to be chemisorbed in a hollow position of C4v symmetry. A recent EELS experiment shows however that in the most stable configuration CO is linearly bonded to the Ni atoms, i.e. a top position of the CO-molecule. This experiment indicates also that there exists an additional bridge bonding of the CO molecule to the two nearest neighbour Ni atoms. The variation of the energy levels, binding energies and charge distribution with the height of the CO molecule above the nickel surface is calculated for the top position using the NiCO and Ni5CO clusters and for the bridge bonding configuration using the Ni2CO cluster. The CO 1π level is found to be split by about 0.8 eV in bridge bonding geometry. For both hollow and top positions the 1π and 5σ levels are separated by about 0.5 eV. The energy separation to the 4σ level is about 3 eV, which is in good agreement with experimental data. Theoretical ionization energies relative to the Fermi energy for top position geometry at a bond distance of 3.5 au between the carbon atom and nickel surface were found to be 25.7, 11.7, 8.7 and 8.2 eV for the 3σ, 4σ, 5σ and 1π levels which should be compared with the experimental data of 29.0, 10.8, 8.4 and 7.8 eV, respectively. The corresponding ionization energies for a bond angle of 99° in bridge bonding were 23.7, 12.1, 7.3, 7.0 and 7.9 eV. The two last values represent the 1π level which is split into two levels in this geometry. The variation of the C-O stretch vibrational frequencies with the height of the CO molecule above the surface for the top-position geometry is estimated from the 5σ and 2π gross orbital populations and from the CO σ and π overlap populations.
AB - Self-consistent Hartree-Fock-Slater molecular cluster calculations for the chemisorption of carbon monoxide on a Ni(100) surface are presented. In earlier calculations of this type the CO molecule has been assumed to be chemisorbed in a hollow position of C4v symmetry. A recent EELS experiment shows however that in the most stable configuration CO is linearly bonded to the Ni atoms, i.e. a top position of the CO-molecule. This experiment indicates also that there exists an additional bridge bonding of the CO molecule to the two nearest neighbour Ni atoms. The variation of the energy levels, binding energies and charge distribution with the height of the CO molecule above the nickel surface is calculated for the top position using the NiCO and Ni5CO clusters and for the bridge bonding configuration using the Ni2CO cluster. The CO 1π level is found to be split by about 0.8 eV in bridge bonding geometry. For both hollow and top positions the 1π and 5σ levels are separated by about 0.5 eV. The energy separation to the 4σ level is about 3 eV, which is in good agreement with experimental data. Theoretical ionization energies relative to the Fermi energy for top position geometry at a bond distance of 3.5 au between the carbon atom and nickel surface were found to be 25.7, 11.7, 8.7 and 8.2 eV for the 3σ, 4σ, 5σ and 1π levels which should be compared with the experimental data of 29.0, 10.8, 8.4 and 7.8 eV, respectively. The corresponding ionization energies for a bond angle of 99° in bridge bonding were 23.7, 12.1, 7.3, 7.0 and 7.9 eV. The two last values represent the 1π level which is split into two levels in this geometry. The variation of the C-O stretch vibrational frequencies with the height of the CO molecule above the surface for the top-position geometry is estimated from the 5σ and 2π gross orbital populations and from the CO σ and π overlap populations.
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U2 - 10.1016/0039-6028(79)90324-8
DO - 10.1016/0039-6028(79)90324-8
M3 - Article
AN - SCOPUS:0001758910
SN - 0039-6028
VL - 82
SP - 139
EP - 164
JO - Surface Science
JF - Surface Science
IS - 1
ER -