Showing papers by "John B. Pendry published in 1989"
216 citations
TL;DR: A technique is presented for embedding planar defects such as interfaces or surfaces in an otherwise perfect crystal, in which a solid containing the defect is first partitioned into layers of atoms.
Abstract: A technique is presented for embedding planar defects such as interfaces or surfaces in an otherwise perfect crystal. The method is a layer Korringa-Kohn-Rostoker scheme, in which a solid containing the defect is first partitioned into layers of atoms. The scattering properties of each layer are calculated in a partial-wave basis set, using the two-dimensional symmetry assumed to be present in each layer. The layers are subsequently coupled together, in a plane-wave basis, to form a solid. The self-consistent equations for the scattering matrices of semi-infinite bulk regions embedding the defect are solved iteratively, removing the constraint of three-dimensional translational symmetry. Within this formalism, ``supercell'' and ``slab'' boundary conditions can also be applied with no extra difficulty. The approach is illustrated in detail for a twin fault in aluminum, for which the microscopic origins of the stacking-fault properties are discussed. Changes in local symmetry and the resulting hybridization of electronic states explain the observed perturbations in the stacking-fault electronic structure.
107 citations
TL;DR: Tensor LEED as discussed by the authors is a perturbative approach to the calculation of LEED I-V spectra in which an initial reference surface is distorted to generate a particular trial structure.
95 citations
TL;DR: Tensor LEED is applied to the structure determination of three model surfaces; a hypothetical p(2 × 2) reconstruction of Ni(100), Cu(100) and a disordered monolayer of O on W(100).
63 citations
TL;DR: In this paper, the authors present the theory and implementation of the new Tensor LEED technique for the rapid calculation of LEED I/V spectra, where a complex trial surface structure is considered as a distortion of a (simpler) reference surface.
29 citations
TL;DR: In this paper, the influence of adatom-adatom interactions on the local structure and reactivity of carbon on the Ni(111) surface was investigated and it was found that carbon strongly repels Ni valence electrons, locally depleting the surface electronic charge density.
19 citations
TL;DR: In this paper, the separate ingredients known to be important in positronium formation, such as band structure, surface effects, matrix elements, scattering of the incoming positron wave and higher order contribution due to interaction of positrons with a remaining hole at the surface beyond the golden rule are drawn together within a single dynamic formalism with the objective of finding a rapid method of calculation.
16 citations
TL;DR: In this paper, the authors focus on the reflection coefficient, a closely related quantity, and suggest a novel formulation of the problem in terms of transfer matrices, which can be calculated explicitly and, although in principle of infinite dimensions, can be approximated by a truncated form.
Abstract: The transmission of waves through disordered media has received much attention in the context of electrical conduction, and numerous techniques have been brought to bear on the problem. Here the authors focus on the reflection coefficient, a closely related quantity. The change in reflectivity on adding a new element to a disordered chain can be calculated by a recursion formula. This in turn suggests a novel formulation of the problem in terms of transfer matrices. These new matrices can be calculated explicitly and, although in principle of infinite dimensions, can be approximated by a truncated form. Using this tool they show how some problems can be solved exactly and how an accurate perturbation expansion can be made for others.
9 citations
TL;DR: In this article, local density of states (LDOS) calculations have been performed on bulk and surface carbides of iron, nickel and copper, and it is concluded that a carbide layer is unstable on copper surfaces, with respect to graphite.
Abstract: Local density of states (LDOS) calculations have been performed on bulk and surface carbides of iron, nickel and copper. Foccussing on the splitting of the carbon p-orbitals and the degree of filling of the anti-bonding p-orbital, we conclude that the stability of the bulk carbides decreases from iron to nickel to copper, in agreement with experimentally known fact. This trend is also observed in the surface carbides, and it is concluded that a carbide layer is unstable on copper surfaces, with respect to graphite. The implications of these results for the mechanism and selectivity in Fischer-Tropsch synthesis on these metals is discussed. Using ideas from Effective Medium Theory, we have also examined the behaviour of various carbon layers on a Ni(111) surface, with a view to examining the mechanism for carbide to graphite transformation. Some preliminary results are presented here.
3 citations
TL;DR: In this article, the authors used the theory of the symmetric group to construct a generalised transfer matrix from which they can obtain the Lyapunov exponents of the original transfer matrix and the localisation lengths for an electron in a random potential.
Abstract: The authors use the theory of the symmetric group to construct a generalised transfer matrix from which they can obtain the Lyapunov exponents of the original transfer matrix and the localisation lengths for an electron in a random potential They compare their results with those of numerical simulations The generalised transfer matrix has infinite dimensions but can in practice be truncated to finite dimensions In the limit of an infinite matrix the theory is exact
1 citations
TL;DR: In this article, the authors explored the sensitivity of diffuse low energy electron diffraction (DLEED) to structural parameters, particularly to the lateral positioning of surface atoms, and concluded that its sensitivity is uniform over a wide range of data.