PROGRAM SUMMARY
Title of program:
REOS99
Catalogue identifier:
ADLF
Ref. in CPC:
124(2000)340
Distribution format: tar gzip file
Operating system: IBM AIX 4.1.2+, Linux 6.1
High speed store required:
20MK words
Number of bits in a word:
32
Peripherals Required: disc
Number of lines in distributed program, including test data, etc:
140885
Keywords:
Atomic physics, Structure, Spectra, Determinant basis,
Einstein coefficients, Electron rearrangement, Lifetimes,
Multiconfiguration, Dirac-Fock, Relativistic, Oscillator strength.
Programming language used: Fortran
Computer:
IBM RS 6000 ,
PC Pentium II .
Other versions of this program:
Cat. Id. Title Ref. in CPC ADEJ REOS 99(1997)323
Nature of physical problem:
Transition probability calculations for (open-shell) atoms have shown
that large wave function expansions are often needed to obtain
sufficient accurate results. For ab-initio calculations, these wave
functions must include the effects of relativity, electron correlations,
and the rearrangement of the electron density within a common framework.
The REOS99 program accounts for all of these effects for the computation
of Einstein coefficients, oscillator strengths, and (radiative)
lifetimes. It applies relativistic wave functions from the GRASP92
package [2] which need subsequently to be expanded into a determinant
basis [3] in order to apply them to REOS99.
Reasons for the new version
Wave function expansions based on several ten thousand determinants and
the computation of large transition arrays made a number of major
modifications in the source code mandatory. Thereby, considerable
improvements have been achieved by taking advantage of the new ANSI
Fortran 90/95 standard. Many powerful features of this up-dated
language like modules, derived data types, dynamic allocation and
deallocation of memory, and others have been exploited in order to
develop a revised version which is forearmed for transition probability
calculations into the next decade. Efficiency has been gained in
particular due to a bitwise storage and treatment of the occupation
numbers of the determinants and due to a parallel computation of all
transitions and multipole components. The bitwise representation of
occupation numbers is maintained by using the bit manipulation
procedures of the Fortran 90/95 standard.
Restrictions on the complexity of the problem
None. A few minor limitations arise for atoms with an open f-shell from
the available list of the coefficients of fractional parentage (cfp) in
GRASP92 which has fully been implemented only for subshells with j<=7/2.
Unusual features of the program
REOS99 is designed for interactive use. Following the interactive
dialog at the beginning of the execution, a number of optional branches
can be selected for the computation of transition probabilities. Two
important branches are the pre-calculation of all radial integrals (as
default) and an assumed orthogonality between the orbitals of the
initial and final atomic states. Of course, the latter branch neglects
a large part of the rearrangement effects of the bound-state density
since all "overlap" contributions are omitted from the computations;
however, this branch may result in a faster execution and may therefore
be attractive for certain applications. A furher acceleration has been
achieved by introducing a cut-off parameter to neglect the contributions
of the (many-electron) matrix elements for those pairs of determinants
for which the product of the mixing coefficients is smaller than a given
value; the default cut-off is set to 10**-8 but can be overwritten
interactively. In addition, individual transitions which need to be
specified by the level numbers of the initial and final atomic states
can be selected. The REOS99 program has entirely been rewritten in line
with the ANSI standard Fortran 90/95 [4]; in particular all language
features which are considered to become obsolete by the standard have
been avoided.
All real variables are parametrized by a selected kind parameter and,
thus, can easily be adapted to any required precision as supported by
the compiler. Presently, the kind parameter is set to double precision
(two 32-bit words) in the module rabs_constant.
The distribution file includes the code for the program CESD99 (Comput.
Phys. Commun. 124(2000)353).
Typical running time
78 minutes on a 266 MHz Pentium II processor
References
[1] S. Fritzsche and C.F. Fischer, Comput. Phys. Commun. 99 (1997) 323.
[2] F.A. Parpia, C.F. Fischer and I.P. Grant, Comput. Phys. Commun.
94 (1996) 249.
[3] S. Fritzsche and I.P. Grant, Comput. Phys. Commun. 103 (1997) 277.
[4] M. Metcalf and J. Reid, Fortran 90/95 Explained (Oxford University
Press, 1996).