Adsorption sites and ligand effect for CO on an alloy surface: a direct view

Y. Gauthier1, M. Schmid2, S. Padovani1, E. Lundgren2, V. Bus3, G. Kresse4, J. Redinger5, P. Varga2

1 Laboratoire de Cristallographie, CNRS, BP 166 X, F-38042 Grenoble Cedex 09, France
2 Institut für Allgemeine Physik, Technische Universität Wien, A-1040 Wien, Austria
3Institute of Physical Engineering, Brno University of Technology, CZ-61669 Brno, Czech Republic
4 Institut für Materialphysik, Universität Wien, Sensengasse 8, A-1090 Wien, Austria
5 Center for Computational Materials Science, E158, Technische Universität Wien, A-1060 Wien, Austria

Phys. Rev. Lett. 87 (2001) 036103

CO adsorption on a PtCo(111) surface has been studied by scanning tunneling microscopy (STM). Comparison of images with chemical contrast of Pt and Co and images showing the CO molecules indicates that CO resides exclusively on top of Pt sites and never on Co. CO bonding is highly sensitive to the chemical environment. The probability to find CO on a Pt atom increases drastically with the number of its Co nearest-neighbors. Ab-initio calculations show that this ligand effect is due to different positions of the center of the Pt d-band.

Corresponding author: M. Schmid (schmid< encoded email address >).

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