Degree Type

Dissertation

Date of Award

2004

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Mark S. Gordon

Abstract

This dissertation consists of two closely related parts: theory development and coding of correlation effects in a model potential for solvation, and study of solvent effects on chemical reactions and processes.;The effective fragment potential (EFP) method has been re-parameterized, using density functional theory (DFT), more specifically, the B3LYP functional. The DFT based EFP method includes short-range correlation effects; hence it is a first step in incorporating the treatment of correlation in the EFP solvation model. In addition, the gradient of the charge penetration term in the EFP model was derived and coded. The new method has been implemented in the electronic structure code GAMESS and is in use. Formulas for the dynamic dipole polarizability, C6 dispersion coefficient and dispersion energy were derived and coded as a part of a treatment of the dispersion interactions in the general solvation model, EFP2. Preliminary results are in good agreement with experimental and other theoretical data.;The DFT based EFP (EFP1/DFT) method was used in the study of microsolvation effects on the SN2 substitution reaction, between chloride and methyl bromide. Changes in the central barrier, for several lowest lying isomers of the systems with one, two, three and four waters, were studied using second order perturbation theory (MP2), DFT and mixed quantum mechanics (QM)/(EFP1/DFT) methods. EFP1IDFT is found to reproduce QM results with high accuracy, at just a fraction of the cost.;Molecular structures and potential energy surfaces for IHI- • Arn (n = 1--7) were studied using the MP2 method. Experimentally observed trends in the structural arrangement of the Ar atoms were explained through the analysis of the geometrical parameters and three-dimensional MP2 molecular electrostatic potentials.

DOI

https://doi.org/10.31274/rtd-180813-12897

Publisher

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

Copyright Owner

Ivana Adamovic

Language

en

Proquest ID

AAI3145626

File Format

application/pdf

File Size

160 pages

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