THIS INFORMATION IS OBSOLETE AND IS PROVIDED ONLY FOR ITS HISTORICAL VALUE

by Donald E. Williams, Department of Chemistry, University of Louisville, Louisville, Kentucky 40292

FORTRAN program PDM87 finds optimized values for atomic charges, dipoles and/or quadrupoles by fitting the surrounding molecular electric potential. Nonatomic sites such as bond sites or one-pair electron sites may also be used. The mathematical method for site charges is described by Williams and Yan (1988) and for site dipoles and quadrupoles by Williams (1988). 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 has been calculated by program Gaussian 80/USF (QCPE 446), but the input format can easily be modified. An ancillary program is provided to interface input/output to the G80USF program. In the most detailed calculation, site monopoles, dipoles and quadrupoles are optimized simultaneously by least squares. Bonds to hydrogen atoms may optionally be foreshortened if desired. A detailed example calculation is given for methanol. A separate program, PDBOND, automatically generates bond centers from the same atomic site input file as PDM87 to find optimum bond dipoles to fit the electric potential. __________

References:

D. W. Williams and J. Yan, Advances in Atomic and Molecular Physics, 23, 87 (1988). D. E. Williams, Journal of Computational Chemistry (submitted, 1988). __________

FORTRAN 77 (VAX) Lines of Code: 2498