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Manuscript Title: Inter-electron repulsion integrals for three-open-shell configurations in cubic symmetry.
Authors: B. Bird, C. Daul, P. Day
Program title: TRIO
Catalogue identifier: AAKT_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 14(1978)273
Programming language: Fortran.
Computer: IBM 370-145.
Operating system: OS/VS1 R 06.0.
RAM: 140K words
Word size: 8
Peripherals: disc.
Keywords: Molecular physics, Quantum chemistry, Theoretical method, Molecular physics, Quantum chemistry, Theoretical method, Electrostatic repulsion, Integral, Irreducible tensor Method, Racah v, w, x coefficient, Fractional parentage Coefficient.
Classification: 16.10.

Nature of problem:
Molecules of high symmetry containing incompletely filled electronic shells, such as transition metal complexes, have excited states whose energies are determined by differences in one-electron orbital energies and changes in electron repulsion energy as the electrons are rearranged on going from the ground to the excited states. This program calculates the contribution of electron repulsion to the energies of electronic-states containing three open shells. It is especially useful for charge transfer configurations.

Solution method:
The vector coupling technique is used to express the repulsion integrals in the strong field scheme as a linear combination of reduced matrix elements which can not be further reduced by symmetry.

Restrictions:
Only shells with different symmetries can be calculated, except for those spanning the irreducible representation t2(gamma5), in which case two shells may have the same symmetry.

Running time:
42 s compilation time, 0.5 s for diagonals and 0.1 for non-diagonal matrix elements.