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Manuscript Title: IPPP: a program for the RPA calculation of transmission mechanisms of spin-spin coupling constants.
Authors: A.R. Engelmann, M.A. Natiello, G.E. Scuseria, R.H. Contreras
Program title: IPPP
Catalogue identifier: AAFL_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 39(1986)409
Programming language: Fortran.
Computer: IBM 370/158.
Operating system: VM/CMS.
RAM: 1528K words
Word size: 32
Keywords: Quantum chemistry, Molecular physics, Structure, Nmr transmission mechanisms - RPA - INDO - IPPP.
Classification: 16.1.

Nature of problem:
The IPPP program calculates NMR spin-spin coupling constants in molecular systems, based on a standard INDO computation, within the RPA (or CHF) approximation solved by the polarization propagator technique. The transmission mechanisms are analyzed by the inner projection of the propagator matrix.

Restrictions:
1. The ground state of the molecular system under study must be a closed-shell restricted Hartree Fock state.
2. The number of orbitals and excitations are limited to: 53 atomic orbitals, 35 doubly occupied (or virtual) molecular orbitals and 315 proper excitations (occupied orbitals * virtual orbitals).

Running time:
The ethylene test run takes 3 sec. for the INDO segment and 19 sec. for the IPPP segment on an IBM 370/158.