CompAS

The international collaboration on Computational Atomic Structure

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Software

GRASP2K

GRASP2K [1] is a collection of programs designed primarily for large scale relativistic calculations based on multiconfiguration Dirac-Hartree-Fock theory [2]. It is a modification and extension of the GRASP92 package by F.A. Parpia, C. Froese Fischer and I.P. Grant [3]. By an extensive use of default options together with a naming convention for the files, the package has been made more user friendly with less input data for the typical case. In most applications, a large number of non-default options can still be invoked when the need arises. A number of large scale calculations have been done and, by an analysis of the CPU utilization, several suboptimal routines were identified. The latter have been rewritten, improving both the speed of execution and, for the relativistic self-consistent field program, the stability. The package implements a biorthogonal transformation method that permits initial and final states in a transition array to be optimized separately, which, in many cases, leads to more accurate values of the resulting rates [4]. In addition to energy structures and transition rates a number of other properties such as hyperfine structure, isotope shift and splittings in external magnetic fields can be computed [5].

ATSP2K

ATSP2K is a MCHF atomic-structure package based on dynamic memory allocation, sparse matrix methods, and a recently developed angular library [6]. It is meant for large-scale calculations in a basis of orthogonal orbitals for groups of LS terms of arbitrary parity. For Breit Pauli calculations, all operators - spin orbit, spin other orbit, spin spin, and orbit orbit - may be included. For transition probabilities the orbitals of the initial and final state need not be orthogonal. A bi-orthogonal transformation is used for the evaluation of matrix elements in such cases. In addition to transition rates of all types, isotope shifts and hyperfine constants can be computed as well as g factors.

SPHF

The B-spline Hartree-Fock program [7], written in FORTRAN95, has many advanced improvements. The usual system of differential equations is replaced by a system of matrix generalized eigenvalue problems, one for each orbital. Orthogonality is dealt with completely through matrix operations. Newton-Raphson methods can be used to avoid convergence problems or for quadratic convergence when varying several orbitals simultaneously. Excited states may be computed as well as Rydberg orbitals in a fixed potential. To improve efficiency, results from low-order splines on a coarse grid can be mapped to splines of higher order on a refined grid.

RATIP

During the past decade, the RATIP program [8] has been developed to calculate the electronic structure and properties of atoms and ions. This code, which is now organized as a suite of programs, provides a powerful platform today to generate and evaluate atomic data for open-shell atoms, including level energies and energy shifts, transition probabilities, Auger parameters as well as a variety of excitation, ionization and recombination amplitudes and cross sections. Although the RATIP program focus on properties with just one electron within the continuum, recent emphasis was placed also on second-order processes as well as on the combination of different types of transition amplitudes in order to explore more complex spectra.

  1. P. Jönsson, G. Gaigalas, J. Bieron, C, Froese Fischer and I.P. Grant, Comput. Phys. Commun., 184 2197 (2013).
  2. P. Jönsson, X. He, C. Froese Fischer and I.P. Grant, Comput. Phys. Commun., 177 (2007) 597.
  3. F.A. Parpia, C. Froese Fischer, I.P. Grant, Comput. Phys. Commun., 94 (1996) 249.
  4. J. Olsen , M. Godefroid, P. Jönsson, P.Å. Malmqvist and C. Froese Fischer, Phys. Rev. E 52 (1995) 4499.
  5. M. Andersson and P. Jönsson, Comput. Phys. Commun., 178 (2008) 156.
  6. C. Froese Fischer, G. Tachiev, G. Gaigalas and M. Godefroid, Comput. Phys. Commun., 176 559 (2007).
  7. C. Froese Fischer, Comput. Phys. Commun., 182 1315 (2011).
  8. S. Fritzsche, Comput. Phys. Commun., 183 1525 (2012).