G E N C L

A code for GEN-eration of C-onfiguration state function L-ists

• Modern fortran version of gencsl(f), based on latest ATSP2K version [3].
• Development version -- use with caution!

This program computes all possible couplings for each member of the reference set, generates all unique, possible configurations and their couplings from the active set, and for each replacement, generates configurations and their couplings, then outputs the configurations and couplings with given final term(s).

Version History (pre-git)

Authors	Year	Version description
C. Froese Fischer and Bin Liu	1983	Original Version, published 1991 [1,2]
G. Gaigalas	1997	Added support for f-shells
J. Grumer	2015	Cleaned and re-implemented in modern Fortran

Description (from [1])

Nature of problem:

In configuration interaction calculations as well as variational MCHF calculations, the wave function is expanded in terms of configuration state functions. In complex atoms, the configuration state lists are best generated systematically according to rules. The present program embodies several rules which have been found useful in dealing with the problem of correlation.

Solution method:

The notion of a complex [4] and single and double replacements are two important concepts that have evolved from the study of correlation in many-electron systems. By systematically generating all couplings of a set of electrons or by considering all possible replacements, this program generates configuration state lists in the "clist" format required by the MCHF atomic structure package [2].

Restrictions:

A maximum of 5 (five) subshells (in addition to the common closed shells) is allowed in any given configuration state and no more than 15 electrons in each of the different sets that are created. These restrictions may be removed by changing dimension statements and some format statements and, in the case of the active set, the code will have to be extended.

I/O

Input: (Interactive)

1. Header
2. List of closed shells
3. The "reference" set
4. The "active" set
5. Replacements from the reference set * Virtual set if replacement is 's' or 'd' or 'sd'
6. Final Term

Output:

1. Header
2. List of closed shells
3. Configurations and their couplings

References

• [1] C. F. Fischer and Bin Liu, Computer Physics Communications, 64, 406 (1991)
• [2] C. F. Fischer et al, Computer Physics Communications, 64, 369 (1991)
• [3] C. F. Fischer et al, Computer Physics Communications, 176, 559 (2007)
• [4] D. Layzer, Ann. Phys. 8, 271 (1959)