Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 49: Metal substrates: Adsorption of organic / bio molecules VI

O 49.3: Talk

Wednesday, March 16, 2011, 15:30–15:45, PHY C213

Elucidating the adsorption mechanism of isophorone on the Pd(111) surface — •Wei Liu, Aditya Savara, Wiebke Ludwig, Swetlana Schauermann, Xinguo Ren, Alexandre Tkatchenko, Hans-Joachim Freund, and Matthias Scheffler — Fritz-Haber-Institut der MPG

We present a joint theoretical and experimental study of the structural, vibrational, and chemical properties of isophorone (C₉H₁₄O) on the Pd(111) surface. Experimental vibrational spectroscopy and temperature-programmed desorption data indicate that both the pure isophorone and dehydrogenated moieties coexist on the surface below 400 K. To elucidate the underlying adsorption and dehydrogenation processes, we carried out density-functional theory (DFT) calculations with and without accounting for the long-range van der Waals (vdW) interactions. The PBE+vdW method [1] significantly changes the potential energy surface compared to the standard PBE, altering both the height and the tilt angle of the molecule with respect to the surface. We identify the reaction pathway from the weakly chemisorbed C₉H₁₄O gas-phase reactant to the strongly chemisorbed dehydrogenated products, both by a direct elimination of hydrogen atoms closest to the Pd(111) surface and by ab initio molecular dynamics simulations. The coexistence of different isophorone moieties on the Pd(111) surface is attributed to an interplay of covalent and van der Waals bonding, along with zero point motion, and kinetic effects.

[1] A. Tkatchenko and M. Scheffler, Phys. Rev. Lett. 102, 073005 (2009).