Degree Type

Dissertation

Date of Award

1993

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Mark S. Gordon

Abstract

The doctoral research concentrates on novel bonding in several chemical systems and parallelization of ab initio codes. The specific chemical processes under consideration are the pseudorotation of pentacoordinated silicon anions of the form SiH[subscript]nX[subscript]5-n[superscript]- where X = F or Cl and n = 0-5, the pseudorotational potential energy surface of PH[subscript]4F, the [pi]-bond strengths in H[subscript]2X=YH[subscript]2 where X = Ge or Sn and Y = C, Si, Ge, or Sn, and the geometries and proton affinities of a series of azaphosphatrane molecules of the form ZP[NR(CH[subscript]2)[subscript]2] [subscript]3N where Z = unsubstituted, H[superscript]+, F[superscript]+, Cl[superscript]+, O, OH[superscript]+, NH, NH[subscript]2[superscript]+, CH[subscript]2, CH[subscript]3[superscript]+ and R = H, CH[subscript]3;The azaphosphatrane studies are performed using the parallel version of the ab initio code GAMESS, showing that use of parallel codes allows theoreticians to produce results in a timely fashion and to facilitate communication and collaboration with experimentalists. The parallel research has produced parallel SCF (RHF, UHF, ROHF, and GVB) energies and gradients and new algorithms for the parallelization of SCF analytic hessians and GUGA MCSCF energies. The former is a small scale algorithm which sends different computational kernels to different subsets of processors. The latter includes a parallel transformation which requires no communication between processors and scales well when the transformation and the diagonalization steps are the main bottlenecks for the MCSCF energy calculation.

DOI

https://doi.org/10.31274/rtd-180813-12916

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Theresa Lynn Windus

Language

en

Proquest ID

AAI9414037

File Format

application/pdf

File Size

315 pages

Share

COinS