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Manuscript Title: A general multiconfiguration Hartree-Fock program.
Authors: C.F. Fischer
Program title: MCHF_88
Catalogue identifier: ABZX_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 64(1991)431
Programming language: Fortran.
Computer: VAX 11/780.
Operating system: VMS, Sun UNIX.
RAM: 96K words
Word size: 32
Peripherals: disc.
Keywords: Atomic physics, structure, Configuration Interaction, energy levels, Ls terms, Complex atoms, functions wave, Bound states, Correlation.
Classification: 2.1.

Subprograms used:
Cat Id Title Reference
ABZU_v1_0 MCHF_LIBRARIES CPC 64(1991)399

Nature of problem:
This program is part of the MCHF atomic structure package [1] for bound state systems. It determines non-relativistic, numerical radial functions and expansion coefficients in the multiconfiguration approximation.

Solution method:
The self-consistent field method is used to solve the system on non- linear differential equations that define the stationary energy of a multiconfiguration expansion, coupled to the secular problem for the expansion coefficients, as described in [2]. Some non-orthogonal orbitals are allowed. A rotation analysis is performed to determine cases where the radial functions may not be unique and, in other cases, to assist convergence to a solution stationary with respect to rotations.

Restrictions:
The most severe restrictions are convergence problems. When one shell is full and the other "almost full", the problem is ill-posed. Also, since the program is meant for bound states, convergence will not be obtained if there is no positive binding for a subshell at the MCHF approximation level. Otherwise, the restrictions are those of the atomic structure package.

Unusual features:
The present version of the program can be used either interactively or in batch mode. Unlike earlier versions, sparse arrays have been replaced by data structures that need to be searched for specific elements, adding some overhead but greatly reducing the memory requirements and relaxing the limits on the orbital quantum number to l<=10.

Running time:
The CPU time required for the first test run is 184.8 seconds for the first stage and 1703.7 seconds for the second on a SUN 3/160 with a floating point board. For the second test run, the Hartree-Fock calculation required 19.8 seconds and the MCHF calculation 41.5 seconds on the same computer system.

References:
[1] C. Froese Fischer, Computer Phys. Commun. 64(1991)369.
[2] C. Froese Fischer, Computer Phys. Reports 3(1986)273.