AVS 51st International Symposium
    Surface Science Monday Sessions
       Session SS1-MoA

Paper SS1-MoA9
Furan Decomposition Mechanism on Vicinal Pd(111) Studied by STM and DFT@footnote 1@

Monday, November 15, 2004, 4:40 pm, Room 210B

Session: Simulation and Theory of Adsorption
Presenter: A. Loui, University of California, Davis
Authors: A. Loui, University of California, Davis
C.Y. Fong, University of California, Davis
S. Chiang, University of California, Davis
Correspondent: Click to Email
We have used scanning tunneling microscopy to investigate the behavior of furan (C@sub 4@H@sub 4@O) adsorbed intactly on stepped Pd(111) at 199 and 225 K, as well as aspects of its decomposition after heating to a maximum temperature of 415 K. Studies conducted on two substrates with relatively narrow and wide terraces reveal strikingly different behaviors. Furan is shown to preferentially adsorb at step edge sites on both surfaces, while evidence of molecular diffusion is seen only on the narrower vicinal planes. After heating to 288 K, 300 K, and 415 K, evidence of reaction can be observed in occupied-states STM images. Our observations support a furan decomposition mechanism wherein the heterocycle preferentially adsorbs and reacts at upper step edge sites. Although our data do not provide a complete picture of the surface reaction, the proposed model is consistent with previous studies of surface adsorption, diffusion, and reaction on vicinal, low-Miller-index transition metal surfaces. Ab initio calculations based on Hohenberg-Kohn density functional theory (DFT) have been performed for several high-symmetry adsorption modes of furan on flat Pd(111). These results, optimized with respect to planewave basis size and k-point sampling of the Brillouin zone, show that a two-fold chemisorption site is energetically preferred over the three-fold hollow and on-top sites. @FootnoteText@ @footnote 1@ Funded by NSF CHE-0111671.