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568. PDM88: Least-Squares Net Atomic Charges or Site
Multipoles from the Surrounding Molecular Electric
Potential (Gaussian-86 Version with Restricted Bond
Dipoles)
by Donald E. Williams, Department of Chemistry,
University of Louisville, Louisville, Kentucky 40292
FORTRAN program PDM88 optimizes values for atomic
charges, dipoles and /or quadrupoles by fitting the
surrounding molecular electric potential. Nonatomic
sites such as bond sites or lone-pair electron sites
may also be used. The mathematical method for site
charges is described by Williams and Yan1 and for site
dipoles and quadrupoles by Williams.2 Bond dipoles
may be restricted to lie along the bond direction. The
input to the program is a list of sites, selection
information about which multipoles are to be optimized,
and a list of points around the molecule where the
electric potential is known. The program anticipates
that the electric potential was calculated by program
GAUSSIAN-863 (which is available from Carnegie-Mellon
University).An ancillary program, G86DGRID, is
provided which reads standard coordinates generated by
GAUSSIAN-86 and selects the potential grid points. In
the most detailed calculation site, monopoles, dipoles
and quadrupoles in any combination are optimized
simultaneously by least squares. Bonds to hydrogen
atoms may optionally be foreshortened if desired. The
program automatically generates bond centers and can
optionally restrict a bond dipole to point along the
bond direction. Additional atomic dipole sites may be
added to the restricted bond dipole model. Standard
deviations and correlation coefficients are calculated.
A detailed example calculation is given for methanol.
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References:
1. D. E. Williams and J. Yan, Advances in Atomic and
Molecular Physics, 23, 87 (1988).
2. D. E. Williams, Journal of Computational Chemistry,
in press (1988).
3. M. Frisch, J. S. Binkley, H. B. Schlegel, K.
Raghavachari, R. Martin, J. P. Stewart, F. Bobrowicz,
D. Defrees, R. Seeger, R. Whiteside, D. Fox, E.
Fluder, and J. A. Pople, GAUSSIAN-86, Release C
(1987), Department of Chemistry, Carnegie-Mellon
University, Pittsburgh, Pennsylvania 15213.
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FORTRAN 77 (VAX)
Lines of Code: 1072
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