title: The atomic structure of low-index surfaces of the intermetallic compound InPd.
abstract: The intermetallic compound InPd (CsCl type of crystal structure with a broad compositional range) is considered as a candidate catalyst for the steam reforming of methanol. Single crystals of this phase have been grown to study the structure of its three low-index surfaces under ultra-high vacuum conditions, using low energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS), and scanning tunneling microscopy (STM). During surface preparation, preferential sputtering leads to a depletion of In within the top few layers for all three surfaces. The near-surface regions remain slightly Pd-rich until annealing to ∼580 K. A transition occurs between 580 and 660 K where In segregates towards the surface and the near-surface regions become slightly In-rich above ∼660 K. This transition is accompanied by a sharpening of LEED patterns and formation of flat step-terrace morphology, as observed by STM. Several superstructures have been identified for the different surfaces associated with this process. Annealing to higher temperatures (≥750 K) leads to faceting via thermal etching as shown for the (110) surface, with a bulk In composition close to the In-rich limit of the existence domain of the cubic phase. The Pd-rich InPd(111) is found to be consistent with a Pd-terminated bulk truncation model as shown by dynamical LEED analysis while, after annealing at higher temperature, the In-rich InPd(111) is consistent with an In-terminated bulk truncation, in agreement with density functional theory (DFT) calculations of the relative surface energies. More complex surface structures are observed for the (100) surface. Additionally, individual grains of a polycrystalline sample are characterized by micro-spot XPS and LEED as well as low-energy electron microscopy. Results from both individual grains and "global" measurements are interpreted based on comparison to our single crystals findings, DFT calculations and previous literature.
authors: Institut Jean Lamour (UMR 7198 CNRS-Université de Lorraine), Parc de Saurupt, F-54011 Nancy Cedex, France.
authors: G M
authors: GM
authors: McGuirk
authors: Institut Jean Lamour (UMR 7198 CNRS-Université de Lorraine), Parc de Saurupt, F-54011 Nancy Cedex, France.
authors: J
authors: J
authors: Ledieu
authors: Institut Jean Lamour (UMR 7198 CNRS-Université de Lorraine), Parc de Saurupt, F-54011 Nancy Cedex, France.
authors: É
authors: É
authors: Gaudry
authors: Institut Jean Lamour (UMR 7198 CNRS-Université de Lorraine), Parc de Saurupt, F-54011 Nancy Cedex, France.
authors: M-C
authors: MC
authors: de Weerd
authors: Department of Earth and Environmental Sciences, Crystallography Section, Ludwig-Maximilians-Universität München, Theresienstrasse 41, D-80333 München, Germany.
authors: M
authors: M
authors: Hahne
authors: Department of Earth and Environmental Sciences, Crystallography Section, Ludwig-Maximilians-Universität München, Theresienstrasse 41, D-80333 München, Germany.
authors: P
authors: P
authors: Gille
authors: Faculty of Natural Sciences, Institute of Chemistry, Materials for Innovative Energy Concepts, Technische Universität Chemnitz, D-09107 Chemnitz, Germany.
authors: D C A
authors: DC
authors: Ivarsson
authors: Faculty of Natural Sciences, Institute of Chemistry, Materials for Innovative Energy Concepts, Technische Universität Chemnitz, D-09107 Chemnitz, Germany.
authors: M
authors: M
authors: Armbrüster
authors: Department of Chemistry, University of Reading, Reading RG6 6AD, United Kingdom.
authors: J
authors: J
authors: Ardini
authors: Department of Chemistry, University of Reading, Reading RG6 6AD, United Kingdom.
authors: G
authors: G
authors: Held
authors: Diamond Light Source Ltd, Didcot OX11 0DE, United Kingdom.
authors: F
authors: F
authors: Maccherozzi
authors: Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstraße 3, D-91058 Erlangen, Germany.
authors: A
authors: A
authors: Bayer
authors: Surface Science Research Centre and Department of Physics, The University of Liverpool, Liverpool L69 3BX, United Kingdom.
authors: M
authors: M
authors: Lowe
authors: Department of Mathematics and Physics, Lappeenranta University of Technology, P.O. Box 20, FIN-53851 Lappeenranta, Finland.
authors: K
authors: K
authors: Pussi
authors: Department of Physics, Penn State University, University Park, Pennsylvania 16802, USA.
authors: R D
authors: RD
authors: Diehl
authors: Institut Jean Lamour (UMR 7198 CNRS-Université de Lorraine), Parc de Saurupt, F-54011 Nancy Cedex, France.
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authors: Fournée