Showing papers by "John B. Pendry published in 1975"
TL;DR: In this article, a theory of the absorption fine structure starting from theoretically obtained electron-atom scattering phase shifts is presented, where the electron scattering is treated using a spherical wave expansion which takes into account the finite size of the atoms.
Abstract: The extended x-ray absorption fine structure is a consequence of the modification of the photoelectron final state due to scattering by the surrounding atoms. We present a theory of the absorption fine structure starting from theoretically obtained electron-atom scattering phase shifts. The electron scattering is treated using a spherical wave expansion which takes into account the finite size of the atoms. Multiple-scattering effects are included by classifying multiple-scattering paths by their total path lengths. Their effects are quite large but appear to make quantitative but not qualitative changes on the single-scattering contribution. The exceptional case is the fourth shell in fcc or bcc structure, where it is shadowed by the first-shell atom and is profoundly affected by forward scattering due to the first shell. This may account for the anomaly observed experimentally at the fourth-shell radius in metals. A detailed numerical calculation is carried out for copper and is shown to agree quite well with experiment.
808 citations
TL;DR: In this paper, the elastic component of an electron beam outside a surface is calculated and significant attenuation is found in the case of RHEED experiments, explaining an earlier disagreement between theory and experiment observed by Menadue and Colella.
Abstract: Attenuation of the elastic component of an electron beam outside a surface is calculated. Significant attenuation is found in the case of RHEED experiments, explaining an earlier disagreement between theory and experiment observed by Menadue and Colella (see abstr. A9238 of 1972).
107 citations
TL;DR: In this paper, a new condition for the existence of surface states was derived for the crystal having both a mirror plane parallel to the surface, and a center of symmetry, which enables us to show that narrow gaps at the centre and edge of the Brillouin zone contain 0 or 1 surface states, narrow gaps inside the zone can contain 0, 1 or 2 states.
82 citations
TL;DR: In this article, it was shown that agreement of calculated LEED spectra with experiment is subject to multiple coincidences in the vertical adsorbate-substrate spacing, with a periodicity of about 0.7 A.
78 citations
TL;DR: In this paper, a step-by-step procedure for solving electron scattering problems in crystals is proposed, where first scattering for a single atom is calculated, then for a chain of atoms next for a layer of chains and finally for the entire crystal.
Abstract: A step by step procedure is suggested for solving electron scattering problems in crystals. First scattering for a single atom is calculated, then for a chain of atoms next for a layer of chains and finally for the entire crystal. The new method has great speed and flexibility. It is applicable to band structure and LEED calculations and is especially useful in the theory of RHEED.
21 citations
TL;DR: In this paper, the authors present and discuss theoretical techniques that considerably increase the power of dynamical leed calculations, particularly in the layer treatment of surfaces, and they make them especially suitable for surface structural determination.
Abstract: The authors present and discuss theoretical techniques that considerably increase the power of dynamical leed calculations, particularly in the layer treatment of surfaces. Their wide applicability makes them especially suitable for surface structural determination. The layer doubling method is an efficient and accurate way of calculating reflectivities off a stack of identical atomic layers requiring only finite absorption for convergence. Layer summation over surface-induced sublattices avoids the repetition of lengthy summations when the surface has a different two-dimensional unit cell from the substrate. The exploitation of symmetry finally can give spectacular reductions in computing time.
13 citations
TL;DR: The absorption of elastic flux for electrons with energies in the range 0-20 Hartrees (0-500 eV) interacting with tightly bound bands in a crystal was studied in this paper.
Abstract: The absorption of elastic flux for electrons with energies in the range 0-20 Hartrees (0-500 eV), interacting with tightly bound bands in a crystal. The inelastic scattering is usually dominated by conduction and valence bands and varies with energy in a manner substantially independent of the band being excited, asymptotically as E-12/lnE. In close-packed structures the strength of absorption varies only weakly over the unit cell, but for more open structures large variations can be expected from one part of the cell to another. The results are relevant to LEED and photoemission experiments.
9 citations