Low energy ion recoil spectroscopy is a powerful technique for the determination of adsorbate position on metal surfaces. In this study, this technique is employed to compare the adsorption sites of hydrogen and deuterium on Pd(100) by detection of either H or D recoil ions produced by Ne+ bombardment. Comparisons of experimental and Kalypso simulated azimuthal yield distributions show that, at room temperature, both hydrogen isotopes are adsorbed in the fourfold hollow site of Pd(100), however, at different heights above the surface (H-0.20 Å and D-0.25 Å). The adsorbates remain in the hollow site at all temperatures up to 383 K even though they move up to 0.40-0.45 Å above the surface. Density functional theory calculations show a similar coverage dependent adsorption height for both H and D and confirm a real difference between the H and D adsorption heights based on zero point energies.
Bibliographical noteFunding Information:
C. Stampfl and A. Soon gratefully acknowledge support from the Australian Research Council (ARC), the Australian National Computational Infrastructure (NCI), and the Australian Centre for Advanced Computing and Communications (ac3).
Discussion with Professor Bruce V. King is greatly appreciated. Financial support by the Australian Agency for International Development (AusAID) and by the University of Brunei Darussalam (to MAK) is gratefully acknowledged.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry