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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. _________ 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. _________ FORTRAN 77 (VAX) Lines of Code: 1072 |