[en] The past of surface structure determination with low-energy electron diffraction (LEED) will be briefly reviewed, setting the stage for a discussion of recent and future developments. The aim of these developments is to solve complex and disordered surface structures. Some efficient solutions to the theoretical and experimental problems will be presented. Since the theoretical problems dominate, the emphasis will be on theoretical approaches to the calculation of the multiple scattering of electrons through complex and disordered surfaces. 49 refs., 13 figs., 1 tab

No abstract available

No abstract available

[en] By means of an efficient dynamical LEED method, the surface structure of W(110) and W(100) faces are examined. It is found that the W(110) surface maintains the bulk structure, despite the possibility for the top tungsten atoms to settle into sites of higher coordination number. The W(100) face exhibits a possible contraction of the top atomic layer by 0.10 +- 0.10 A. These results fit into a trend correlating a top-layer contraction with the absence of close-packing in the top layer, i.e. with the roughness of the surface. (Auth.)

[en] We investigate the extent of diffraction effects (coherent elastic scattering) in electron spectra measured on materials that do not exhibit perfect crystal structure, such as crystals with a high defect density, polycrystalline materials or even amorphous solids. A single scattering cluster (SSC) model was implemented to calculate photoelectron angular distributions for non-ideal crystals. As a first test, results obtained with this code were compared with a well established code for a perfect crystal. The two codes were found to give essentially identical results. Furthermore, SSC calculations of Ni2s photoelectron depth distributions averaged over crystal orientation so as to apply to an amorphous material were compared with Monte-Carlo (MC) simulations of elastic scattering, entirely based on a non-coherent scattering model. The two sets of results were semi-quantitatively consistent

[en] The temperature dependence of the first three interlayer distances of the Ag(111) surface was studied by low-energy electron diffraction (LEED) over the temperature range 128K to 723 K. The first three interlayer spacings and the effective Debye temperatures were extracted from the LEED analysis. At the lowest temperature, the first two interlayer spacings are slightly (0.5 percent) contracted. All three interlayer spacings increase with temperature, finally reaching expansions relative to the bulk of about 0.8 percent at the highest temperature studied. The effective surface Debye temperature is lowest for the outermost layer, increasing toward the bulk value for successive layers

[en] The temperature dependence of the first three interlayer distances of the Ag(111) surface was studied by low-energy electron diffraction (LEED) over the temperature range 128K to 723 K. The first three interlayer spacings and the effective Debye temperatures were extracted from the LEED analysis. At the lowest temperature, the first two interlayer spacings are slightly (0.5 percent) contracted. All three interlayer spacings increase with temperature, finally reaching expansions relative to the bulk of about 0.8 percent at the highest temperature studied. The effective surface Debye temperature is lowest for the outermost layer, increasing toward the bulk value for successive layers

No abstract available

No abstract available

[en] The local adsorption structure of CO on Co(0001) was determined at 160 K using dynamical low-energy electron diffraction (LEED). The CO molecules in the (root3xroot3) R30 degrees-CO overlayer adopt the on-top site with the CO axis perpendicular to the surface and induce buckling in the top Co layer pulling the Co atom beneath the CO by 0.04 plus or minus 0.04 Angstrom outwards. The optimum length for the CO bond is 1.17 plus or minus 0.06 Angstrom and that for the C-Co distance 1.78 plus or minus 0.06 Angstrom. The first layer Co-Co distance is 2.04 Angstrom and thus only slightly expanded from the bulk value. The obtained structure is compared to other known CO structures on transition metals