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110. OMEGAMO: Hückel Calculations in Which the Input
Matrix Is Modified by Charge Densities and Bond Lengths
by Peter Gund, Amherst University, Amherst,
Massachusetts 01002
This program carries out standard Hückel calculations,
producing the orbital energies, eigenfunctions, total
pi-energy, delocalization energy, bond orders, bond
lengths, and charge densities; provision is made for
calculating new Coulomb integrals, a, from the charge
densities by the w technique, and for calculating new
resonance integrals, b, from a bond length
relationship. The quantities may then be calculated
anew, with iteration to self-consistent energy. The
maximum number of iterations is specified.
A wide range of options includes:
Input of initial bond lengths (in angstroms) or
nonintegral values of the resonance integral, b, in
units of bo. If no value is specified, the value of
1.0b is used.
Input of non-zero values of Coulomb integral, a, for
heteroatoms (units of b).
Use of modified w technique equation for atoms
contributing more than one electron to the pi-system.
Treating acetylenic bonds by correcting the calculated
bond order for the in-plane pi-bond.
ITERFAST procedure for averaging consecutive iterated
values of the charge densities and bond orders to speed
convergence. Suppressing intermediate printout data
until self-consistent value of energy is attained.
Subroutine JACOBI diagonalizes matrix and calculates
eigenfunctions; it is lifted with minor changes from
QCPE 64.
Subroutine ENTOT calculates total pi-energy and
delocalization energy.
Subroutine OMEGA calculates charge densities and
modifies Coulomb integrals, a, by the w technique.
Subroutine BONDO calculates bond orders and lengths,
and modifies resonance integrals, b, correspondingly.
Subroutine PRINTER prints out matrices and is modified
from QCPE 64.
FORTRAN 63
Lines of Code: 452
Recommended Citation: P. Gund, QCPE 11, 110 (1967).
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