Computer Physics Communications Program Library

Programs in Physics & Physical Chemistry

Manuscript Title: An MCHF atomic-structure package for large-scale calculations

Authors: Charlotte Froese Fischer, Georgio Tachiev, Gediminas Gaigalas, Michel R. Godefroid

Program title: ATSP2K

Catalogue identifier: ADLY_v2_0
Distribution format: tar.gz

Journal reference: Comput. Phys. Commun. 176(2007)559

Programming language: FORTRAN 90.

Computer: Pentium III 500 Mhz;.

Operating system: Red Hat 8.

RAM: 256 Mbytes words

Word size: 32 bits

Supplementary material: User manuals for the program ATSP2k and for the Spin-Angular library are available.

Keywords: atomic structure, bound states, Breit-Pauli Hamiltonian, configuration interaction, complex atoms, correlation, gJ values, hyperfine constants, isotope shift, LSJ wavefunctions, transition probabilities.

PACS: 31.15.Ne, 31.24.-v, 32.10.-f, 32.30.-r.

Classification: 2.1.

Does the new version supersede the previous version?: Yes

Nature of problem:
This program determines energy levels and associated wave functions for states of atoms and ions in the MCHF (LS) or Breit-Pauli (LSJ) approximation. Given the wave function, various atomic properties can be computed such as electric (Ek) and magnetic (Mk) multipole radiative transition probabilities (k_max =10) between LS or LSJ states, isotope shift constants, hyperfine parameters, and gJ factors.

Solution method:
The new version of the program closely follows the design and structure of the previous one [1], except that a simultaneous optimization scheme has been introduced. This program uses the angular methodology of [2] and has been extended to include partially filled f-subshells in wavefunction expansions but assumes all orbitals are orthonormal. The biorthogonal transformation method is used to deal with the nonorthogonality of orbitals between initial and final states of an electromagnetic radiative transition.

Reasons for new version:
The previous version of the MCHF atomic structure package [1] was intended for small calculations, ideal for someone not familiar with the code, producing extensive print-out of intermediate results. The codes for the calculation of spin-angular coefficients were often not the most efficient and could only treat configurations with open f-subshells containing at most two electrons or an almost filled shell with one hole. The present version is designed for large-scale computation using algorithms for angular integration that have been shown to be faster, and include the case of arbitrarily filled f-shells. In addition, the MCHF program has been modified to include optimization on an energy functional that is a weighted average of energy functionals for expansions of wavefunctions for different LS terms or parity, thus facilitating Breit-Pauli calculations for complex atomic systems and for computing targets in collision calculations.

Summary of revisions:
Programs have been modified to take advantage of the newly developed angular library [2], extended to arbitrarily filled f-shells. New programs have been developed for simultaneous optimization and for the efficient calculation of atomic spectra and transition rates for an iso-electronic sequence. All applications now take advantage of dynamic menory allocation and sparse matrix methods.

Restrictions:
All orbitals in a wave function expansion are assumed to be orthonormal. Configuration states are restricted to at most eight (8) subshells in addition to the closed shells common to all configuration states. The maximum size is limited by the available memory and disk space.

Unusual features:
The programming style is essentially F77 with extensions for the POINTER data type and associated memory allocation. These have been available on workstations for more than a decade but their implementations are compiler dependent. The present serial code has been installed and tested extensively using both the Portland Group, pgf90, compiler and the IBM SP2, xlf90, compiler. The former is compatible also with the Intel Fortran90 compiler. The MPI codes are included for completeness though testing has not been as extensive.

Additional comments:
Parallel versions (MPI) of the following programs are included in the distribution. Use of these is optional but can speed up the angular integration processing.

Serial	Parallel
nonh	nonh_mpi
mchf	mchf_mpi
bp_ang, bp_mat, bp_eiv	bp_ang_mpi, bp_mat_ang, bp_eiv_mpi
biotr_ang, biotr_tr	biotr_ang_mpi, biotr_tr_mpi

Running time:
Included with the code are scripts for calculating E2 and M1 transitions between levels of 3s²3p² for Si and P⁺. This calculation has two stages: LS and LSJ. The calculation of the former required 21 minutes for the LS calculation and 36.5 minutes for the Breit-Pauli configuration interaction calculation that determines the mixing of the terms.

References:

[1]

C. Froese Fischer, Comput. Phys. Commun. 128 (2000) 635.

[2]

G. Gaigalas, Lithuanian J. Physics 41 (2000) 39.