2004/09/30 by Peter Koval, S. Fritzsche, Stephan Fritzsche
Physics and Astronomy · #Atomic and Molecular Physics #Nuclear physics research studies #Scientific Research and Discoveries #physics.atom-ph #quant-ph
paper · pdf · doi:10.1016/j.cpc.2005.01.023
published as Peter Koval and Stephan Fritzsche, Comput. Phys. Comm. 172 (2005) 187-202 · 20 pages, 1 figure
openalex publication_date 2005/08/27 · arxiv created 2005/11/07 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
From perturbation theory, Green's functions are known for providing a simple and convenient access to the (complete) spectrum of atoms and ions. Having these functions available, they may help carry out perturbation expansions to any order beyond the first one. For most realistic potentials, however, the Green's functions need to be calculated numerically since an analytic form is known only for free electrons or for their motion in a pure Coulomb field. Therefore, in order to facilitate the use of Green's functions also for atoms and ions other than the hydrogen--like ions, here we provide an extension to the Ratip program which supports the computation of relativistic (one--electron) Green's functions in an -- arbitrarily given -- central--field potential \rV(r). Different computational modes have been implemented to define these effective potentials and to generate the radial Green's functions for all bound--state energies E < 0. In addition, care has been taken to provide a user--friendly component of the Ratip package by utilizing features of the Fortran 90/95 standard such as data structures, allocatable arrays, or a module--oriented design.