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Title: Physics of the Be(10{bar 1} 0) Surface Core Level Spectrum

Abstract

Photoelectron diffraction has been utilized to confirm the theoretical prediction that the surface core level shifts observed for Be(10{bar 1}0) have been improperly assigned. The original assignment based upon the relative intensity of the shifted components was intuitively obvious: the peak with the largest shift of {minus}0.7 eV with respect to the bulk was associated with the surface plane, the next peak shifted by {minus}0.5 eV stems from the second layer, and the third peak at {minus}0.22 eV from the third and fourth layers. First-principles theory and our experimental data show that the largest shift is associated with the second plane, not the first plane. {copyright} {ital 1998} {ital The American Physical Society }

Authors:
 [1];  [2];  [1];  [3];  [4];  [2];  [5];  [6]
  1. Sincrotrone Trieste, Trieste (Italy)
  2. Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996 (United States)|[Oak Ridge National Laboratories, Oak Ridge, Tennessee 37831 (United States)
  3. Sincrotrone Trieste, Universit degli Studi di Trieste, Laboratorio TASC-INFM, Trieste (Italy)
  4. Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany)
  5. Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
  6. Institute for Storage Ring Facilities, University of Aarhus, Aarhus (Denmark)|[Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany)|[Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37831 (United States)
Publication Date:
Research Org.:
Oak Ridge National Laboratory
OSTI Identifier:
662304
DOE Contract Number:
AC05-96OR22464
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 81; Journal Issue: 15; Other Information: PBD: Oct 1998
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BINDING ENERGY; BERYLLIUM; ELECTRONIC STRUCTURE; SURFACES; PHOTOELECTRON SPECTROSCOPY; DIFFRACTION; SPECTRAL SHIFT; ANGULAR DISTRIBUTION

Citation Formats

Lizzit, S., Pohl, K., Baraldi, A., Comelli, G., Fritzsche, V., Plummer, E.W., Stumpf, R., and Hofmann, P.. Physics of the Be(10{bar 1} 0) Surface Core Level Spectrum. United States: N. p., 1998. Web. doi:10.1103/PhysRevLett.81.3271.
Lizzit, S., Pohl, K., Baraldi, A., Comelli, G., Fritzsche, V., Plummer, E.W., Stumpf, R., & Hofmann, P.. Physics of the Be(10{bar 1} 0) Surface Core Level Spectrum. United States. doi:10.1103/PhysRevLett.81.3271.
Lizzit, S., Pohl, K., Baraldi, A., Comelli, G., Fritzsche, V., Plummer, E.W., Stumpf, R., and Hofmann, P.. Thu . "Physics of the Be(10{bar 1} 0) Surface Core Level Spectrum". United States. doi:10.1103/PhysRevLett.81.3271.
@article{osti_662304,
title = {Physics of the Be(10{bar 1} 0) Surface Core Level Spectrum},
author = {Lizzit, S. and Pohl, K. and Baraldi, A. and Comelli, G. and Fritzsche, V. and Plummer, E.W. and Stumpf, R. and Hofmann, P.},
abstractNote = {Photoelectron diffraction has been utilized to confirm the theoretical prediction that the surface core level shifts observed for Be(10{bar 1}0) have been improperly assigned. The original assignment based upon the relative intensity of the shifted components was intuitively obvious: the peak with the largest shift of {minus}0.7 eV with respect to the bulk was associated with the surface plane, the next peak shifted by {minus}0.5 eV stems from the second layer, and the third peak at {minus}0.22 eV from the third and fourth layers. First-principles theory and our experimental data show that the largest shift is associated with the second plane, not the first plane. {copyright} {ital 1998} {ital The American Physical Society }},
doi = {10.1103/PhysRevLett.81.3271},
journal = {Physical Review Letters},
number = 15,
volume = 81,
place = {United States},
year = {Thu Oct 01 00:00:00 EDT 1998},
month = {Thu Oct 01 00:00:00 EDT 1998}
}
  • First-principles calculations for slabs as many as 13 layers thick show that the three surface core-level features observed on Be(0001) correspond to core-electron ionizations in its three outermost atomic layers. The calculations also imply that the experimental peak identified with core ionization in the bulk is a composite; theoretical core-ionization potentials for the fourth and deeper layers differ by as much as 90 meV. The sign and surprisingly large magnitudes of the Be(0001) surface core-level shifts (SCLS's) are attributed to unusually large surface-state contributions to the three outer layers' local densities of states. Both initial- and final-state effects are substantialmore » in the SCLS's, and their contributions are additive.« less
  • Temperature-dependent low-energy electron diffraction I-V measurements and density-functional calculations within the quasiharmonic approximation reveal that the Mg(10{bar 1}0) surface exhibits a remarkable oscillatory surface thermal expansion, thermal contraction in the short interlayer, and thermal expansion in the long interlayer. The thermal expansion of the long interlayer is intimately tied to the thermal contraction in the short interlayer in the surface region.
  • Periodic Hartree{endash}Fock total energy calculations on two-dimensionally periodic slabs have been used to predict the equilibrium geometry of a monolayer of carbon monoxide molecules adsorbed on the nonpolar (10{bar 1}0) surface of ZnO. Two physisorbed (or weakly chemisorbed) minimum energy configurations are found. In one the CO molecules adsorb with their oxygen atoms coordinated to surface Zn atoms, while in the other the carbon atoms are coordinated to surface Zn atoms. The two calculated minima are very close in energy. In the second geometry, the C{endash}Zn {open_quote}{open_quote}bond{close_quote}{close_quote} and the C{endash}O bond make angles of 32.5{degree} and 39.5{degree} with the surfacemore » normal, and the intramolecular bond shortens slightly from its free value in reasonable agreement with experimental results. No binding of CO to the surface oxygen atoms is predicted. Surface-related changes in the vibrational frequencies for the adsorbed molecules agree reasonably well with infrared spectroscopic data, and the {open_quote}{open_quote}carbon-down{close_quote}{close_quote} binding energy of the molecule with the surface is in good agreement with thermal desorption data (though electron correlation effects have to be included in the calculation to obtain acceptable results for low surface coverage). {copyright} {ital 1996 American Institute of Physics.}« less
  • The results of a study of the surface relaxation of GaN in the framework of the {ital ab} {ital initio} (all-electron) Hartree-Fock method are presented. We perform total-energy calculations using a two-dimensionally periodic slab model for the most stable nonpolar cleavage faces, namely, the (10{bar 1}0) and (110) surfaces of the wurtzite and zinc-blende phases, respectively. For both surfaces, when the energy is minimized the Ga-N surface bonds show a very small rotation angle of about 6{degree} accompanied by a reduction in surface bond length of about 7{percent}. This result differs from the well-accepted model of the GaP (110) andmore » GaAs (110) surfaces, where there is a large rotational angle in the range of 27{degree}{endash}31{degree} and little change in surface bond length. The structure dependence of the calculated density of states suggests that this difference is at least partly due to interaction of the Ga 3{ital d} states with N 2{ital s}-derived states in GaN. Partial double-bond character in the surface bond may also be important. {copyright} {ital 1996 The American Physical Society.}« less
  • Density functional molecular cluster calculations have been used to study the adsorption of CO and H{sub 2} on the ZnO(10{bar 1}0) surface. Substrate and adsorbate geometry modifications, adsorption energies and adsorbate vibrations are computed in good agreement with experiment. For CO, the influence of Cu surface impurities has been also considered. Despite the limited size of the adopted clusters, surface relaxations computed for the clean and undoped ZnO(10{bar 1}0) agree well with experimental measurements. The chemisorption of CO on ZnO (10{bar 1}0) relieves some of the relaxation of the Lewis acid site (L{sub s}{sup a}); nevertheless, the L{sub s}{sup a}more » electronic structure is negligibly affected by the interaction with CO. At variance to that, the stronger interaction of CO with copper impurities significantly influences both the geometry and the electronic structure of L{sub s}{sup a}, extending its effects to the adjacent Lewis base site (L{sub s}{sup b}). The dissociative adsorption of H{sub 2} is found to be exothermic by 23 kcal/mol, and it implies the L{sub s}{sup a}-L{sub s}{sup b} bond breaking.« less