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443. VESCF: Variable Electronegativity Self-Consistent
Field
by Julia C. Tai, Department of Natural Sciences, The
University of Michigan, Dearborn, Michigan 48128 and N.
L. Allinger, Department of Chemistry, The University of
Georgia, Athens, Georgia 30602
This program calculates the electronic spectra of
molecules up to 24 pi orbitals by a modified Pariser-
Parr method with inclusion of singly and doubly excited
configurations. The molecular orbitals are obtained by
a variable electronegativity self-consistent field
(VESCF) treatment.Detailed procedure and input
parameters used for carbon, nitrogen and oxygen
orbitals are described in the following publications:
1. N. L. Allinger, J. C. Tai, and T. W. Stuart,
Theoretica Chim. Acta, 8, 101 (1967).
2. N. L. Allinger, T. W. Stuart, and J. C. Tai, J. Am.
Chem. Soc., 90, 2809 (1986).
3. J. C. Tai and N. L. Allinger, Theoretica Chim.
Acta, 12, 261 (1868).
4. J. C. Tai and N. L. Allinger, ibid, 15, 133 (1969).
One feature of the program that is not described in any
previous publication is the option to vary the number
of doubly excited configurations that are included in
the final configuration interaction (CI) matrix through
use of the parameter IDELTA.Doubly excited
configurations Vijkl with k+l-(l+j) equal to or greater
than IDELTA will not be included. This option is
introduced for two reasons: 1) to cut down the
computation time, and 2) to reduce the number of
configurations so that the total number in any CI
matrix will not exceed 400 (the upper limit imposed by
the program). It should be noted that the optimum
value of IDELTA to use is currently under
investigation.
FORTRAN IV (IBM)
Lines of Code: 3163
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