Showing papers by "John B. Pendry published in 1971"

Ion core scattering and low energy electron diffraction. I

Abstract: The construction of accurate ion core scattering factors is discussed, and a Hartree-Fock treatment of exchange found to be important. A formalism is constructed for making accurate, fast, nonperturbative calculations of LEED spectra within the framework of the ion core scattering model.

Fast perturbation schemes for low energy electron diffraction spectra

Abstract: A careful analysis is made of the convergence of several perturbative techniques for calculating LEED intensities with the hope of finding a scheme that is both fast and accurate. Carefully calculated scattering factors are used in this analysis. Unfortunately divergence, or poor convergence of the relevant series holds for most theories. However a renormalization for the forward scattering (RFS) results in a highly convergent series (RFS perturbation theory) that is amenable to rapid calculations.

The cancellation theorem in pseudopotential theory

Abstract: The cancellation theorem of Cohen and Heine is derived in an exact form using a phase function approach. The new form of the theorem enables precise statements to be made about how far the zero to which we cancel the potential is arbitrary, and in certain circumstances to detect over cancellation. The latter phenomenon is ascribed to the influence of the core states and an expression derived for the maximum repulsive potential we can expect when we have over cancellation.