Computation of photoelectron and Auger-electron diffraction I. Preparation of input data for the cluster calculation PAD1

We describe the theory and implementation of multiple scattering cluster calculations of angle-resolved core-level photoelectron and Auger-electron diffraction intensities based on a concentric-shell algorithm (CSA). In this paper, we describe the first of a series of three computer programs which implement the calculations. In the present program, sorting algorithms are used to arrange atoms by their symmetry groups and into a series of concentric shells, as required by the CSA. For maximum user-friendliness, all input parameters may be specified in a self-explanatory file, which contains information about the cluster and the experimental parameters.