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Manuscript Title: Diagrammatic many-body perturbation expansion for atoms and molecules: III. Third-order ring energies.
Authors: S. Wilson
Program title: MBPT RING DIAGRAMS
Catalogue identifier: ACXH_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 14(1978)91
Programming language: Fortran.
Computer: IBM 360/91.
Operating system: ASP.
Program overlaid: yes
RAM: 200K words
Word size: 8
Peripherals: disc.
Keywords: Atomic physics, Molecular physics, Electronic, Structure, Diagram, Many-body, Perturbation theory, Third-order, Hole-particle diagram, Ring diagram, Quantum chemistry.
Classification: 2.1, 16.1.

Subprograms used:
Cat Id Title Reference
ACXF_v1_0 MBPT ORGANIZATION CPC 14(1978)71
ACXG_v1_0 MBPT LADDER DIAGRAMS CPC 14(1978)81

Nature of problem:
The non-relativistic Schrodinger equation for the electronic structure of atomic and molecular systems is considered within the Born- Oppenheimer approximation.

Solution method:
The diagrammatic many-body perturbation expansion is employed through third-order in the energy and first-order in the wave function. All many-body terms are evaluated. The calculations are performed within the algebraic approximation in which the one-electron state functions are parameterized by expansion in a finite set of basis functions. Computer algorithms are presented for the evaluation of third-order hole-particle, or ring, diagrams.

Restrictions:
The reference wave function must be a non-degenerate, closed-shell Hartree-Fock determinant. The current program is restricted to systems containing up to twenty electrons described by basis sets containing a maximum of 35 spatial functions. These latter restrictions are easily changed.

Unusual features:
This program is designed for use with those described in the two preced- ing papers C.P.C. 14(1978)71, 14(1978)81.

Running time:
Running times are strongly dependent on the size of the basis set and the number of electrons. Some timing data has been presented previously. The test run requires 1.5 s of CPU time on an IBM 360/91 computer for the execution of the subprograms described in this paper.