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# 1. Introduction

This package is a Python-based implementation of the Barbieri/Van Hove phase shift (phsh) calculation package needed to produce phase shifts for various LEED packages (including CLEED), as well as for certain XPD packages.

To quote the original authors site:

“The phase shift calculation is performed in several steps:

1. Calculation of the radial charge density for a free atom.
2. Calculation of the radial muffin-tin potential for atoms embedded in a surface defined by the user (the surface is represented by a slab that is periodically repeated in 3 dimensions, within vacuum between the repeated slabs); various approximations to the exchange potential are available; relativistic effects are taken into account.
3. Calculation of phase shifts from the muffin-tin potential.
4. Elimination of pi-jumps in the energy dependence of the phase shifts.”

Note

You can get the original Fortran source (& learn more about the phsh programs) from:

> http://www.icts.hkbu.edu.hk/surfstructinfo/SurfStrucInfo_files/leed/leedpack.html

The aim of this package is to both automate and simplify the generation of phase shift files in a manner that is easy for the computational hitch-hiker, but powerful for those that wish to extend the package for particular needs.

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