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Manuscript Title: Diagrammatic many-body perturbation expansion for atoms and moleucles. VIII. ccMBPT-4t.
Authors: D. Moncrieff, V.R. Saunders, S. Wilson
Program title: ccMBPT-4t
Catalogue identifier: ACHN_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 70(1992)345
Programming language: Fortran.
Computer: CRAY X-MP.
Operating system: UNICOS.
RAM: 2700K words
Peripherals: disc.
Keywords: Quantum chemistry, Atomic physics, Molecular physics, Electronic, Structure, Diagram, Many-body, Perturbation theory, Fourth-order, Triple excitations.
Classification: 2.1, 16.1.

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 in fourth- order for the energy. The calculations are performed within the algebraic approximation in which the one-electron state functions are parametrized by expansion in a finite set of basis functions. Algorithms, which exploit a dynamic load balancing technique to execute parts of the computation concurrently, are presented for the evaluation of fourth-order energy components involving triply excited intermediate states.

The reference wave function must be a non-degenerate, closed-shell Hartree-Fock determinant. The current program is restricted to systems containing up to 8 electrons described by basis sets containing a maximum of 65 spatial functions. These restrictions can be changed very easily.

Unusual features:
The program requires lists of two-electron integrals and orbital energies as input.

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 56 seconds of CPU time on a CRAY Y- MP/432 computer for the execution of the programs described in this paper.