Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 3: Adsorption I
O 3.5: Vortrag
Montag, 27. März 2006, 12:15–12:30, TRE Phys
Adsorption modes of ethene on Pt(111) and Cu3Pt(111) from vibrational spectrocopy and DFT calculations — •Conrad Becker, Jan Haubrich, Thomas Pelster, and Klaus Wandelt — Institut für Physikalische und Theoretische Chemie der Universität Bonn, Wegelerstr. 12, 53115 Bonn
The adsorption of ethene on Pt(111) and Cu3Pt(111) at 100K has been investigated experimentally using high resolution electron energy loss spectroscopy (HREELS) and temperature programmed desorption (TPD). The spectra suggest two signifcantly different adsorption modes, which can be characterized as a bridged di-σ-mode on Pt(111) and a more weakly bound atop mode on Cu3Pt(111). Using the Vienna ab initio simulation package (VASP) we have computed the bonding geometries and energies as well as the vibrational spectra of the di-σ-mode and the atop mode. As expected the di-σ-mode is the strongest bonding mode on Pt(111). When the molecule is, however, forced to an atop position - a situation that corresponds to the bonding on the Cu3Pt(111) surface - the most favourable configuration is a metalla cycle, which is characterized by two σ-bonds on a single Pt atom. Furthermore, the adsorption energy of the metalla cycle is significantly smaller than that of the di-σ-mode, which reflects the findings of the TPD experiments. Based on DFT calculations a complete assignment of the modes in the HREELS spectra is performed.