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Manuscript Title: Calculation of LEED diffracted intensities.
Authors: D.J. Titterington, C.G. Kinniburgh
Program title: CAVLEED
Catalogue identifier: ABVB_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 20(1980)237
Programming language: Fortran.
Computer: IBM 370/165.
Operating system: OS MVT.
RAM: 240K words
Word size: 8
Keywords: Solid state physics, Electron diffraction, Leed, Meed, Rheed, Surface structure, Electron scattering, Layer method, Overlayer, Muffin-tin, Lattice sums, Chain method, Perturbation calculation, Layer doubling.
Classification: 7.2.

Revision history:
Type Tit le Reference
correction 000A CORRECTION 09/01/81 See below

Nature of problem:
An electron diffraction experiment on a crystal surface provides a diffraction pattern which reflects the 2-dimensional periodicity of the surface, and also a record of the diffracted beam intensities as a function of incident beam energy and direction. This is compared with theoretical intensity curves calculated on the basis of trial models for the surface structure: a program to compute intensity curves for a wide range of surface models is presented here.

Solution method:
The surface region of the crystal is regarded as being made up of well separated atomic layers parallel to the surface, each containing up to two atoms per unit cell: the layers need not be coplanar. Muffin-tin atomic potentials are assumed, the electron scattering properties of each atom being described by a set of input phase shifts. Multiple scattering between the atoms within a layer is calculated using either direct summation or the chain method. Multiple scattering between layers is included by either the renormalised forward scattering perturbation method or the matrix doubling scheme, to give the wave amplitudes of diffracted beams at the surface.

Restrictions:
Layers may contain either one or two atoms per unit cell. A periodic bulk layer stacking sequence is assumed, and over-layers with lattices simply related to the bulk may also be included. Dimensions of arrays are set up for 6 phase shifts and 21 beams.

CORRECTION SUMMARY
Manuscript Title: Calculation of LEED diffracted intensities. (C.P.C. 20(1980)237).
Authors: D.J. Titterington, C.G. Kinniburgh
Program title: 000A CORRECTION 09/01/81
Catalogue identifier: ABVB_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 22(1981)103
Classification: 7.2.