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ELECTRONIC STRUCTURE AND SPECTROSCOPY IN THE GAS AND
CONDENSED PHASE: METHODOLOGY AND APPLICATIONS.
by
Vitalii Vanovschi
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMISTRY)
May 2009
Copyright 2009 Vitalii Vanovschi
Object Description
| Title | Electronic structure and spectroscopy in the gas and condensed phase: methodology and applications |
| Author | Vanovschi, Vitalii |
| Author email | vvanovsc@usc.edu; vanovsky@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemistry |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2009-01-09 |
| Date submitted | 2009 |
| Restricted until | Restricted until 20 Feb. 2011. |
| Date published | 2011-02-20 |
| Advisor (committee chair) | Krylov, Anna I. |
| Advisor (committee member) |
Wittig, Curt Haas, Stephan |
| Abstract | Method developments and applications of the condensed phase and gas phase modeling techniques are presented in two parts of this work.; In the first part, the theory of the effective fragment potential (EFP) method designed for accurate modeling of the molecular properties of the extended systems is introduced. The implementation of EFP developed in this work within the Q-Chem electronic structure package is discussed in details. The code is applied to the studies of Pi - Pi interactions in benzene oligomers. The primary interest of these studies are the many-body and total non-additive Pi - Pi interactions. A detailed comparison of EFP with ab initio theories is presented for the set of eight benzene trimers. Three-body intermolecular interaction energies at the EFP level of theory are within 0.04 kcal/mol from the full ab initio results. To elucidate the asymptomatic behavior of the total non-additive binding energy, three types of linear benzene oligomers with 10, 20, 30 and 40 monomers are modeled using our new EFP implementation. The result of this investigation is that with the increase in the size of linear benzene clusters, the share of the total non-binding energy approaches a constant and does not exceed 4% for the structures considered in the study. This result indicates that there are no substantial non-local effects in the binding mechanism of linear benzene clusters.; In the second part, the equilibrium structure, vibrational frequencies, and ionization energies of the para-benzyne radical anion are characterized by coupled-cluster and equation-of-motion methods. Vibronic interactions with the low-lying excited state result in a flat potential energy surface along the coupling mode and even in lowersymmetry C2v structures. Additional complications arise due to the Hartree-Fock instabilities and near-instabilities. The magnitude of vibronic interactions was characterized by geometrical parameters, charge localization patterns and energy differences between the D2h and C2v structures. The observed trends suggest that the C2v minimum predicted by several theoretical methods is an artifact of an incomplete correlation treatment. The comparison between the calculated and experimental spectrum confirmed D2h structure of the anion, as well as accuracy of the coupled-cluster and spin-flip geometries, frequencies and normal modes of the anion and the diradical. Density functional calculations (B3LYP) yielded only a D2h minimum, however, the quality of the structure and vibrational frequencies is poor, as follows from the comparison to the high-level wave function calculations and the calculated spectrum. The analysis of charge localization patterns and the performance of different functionals revealed that B3LYP underestimates the magnitude of vibronic interactions due to self-interaction error. |
| Keyword | effective fragment potential; benzene clusters; para-benzyne radical anion; photoelectron spectroscopy; coupled-cluster methods; density functional theory; symmetry breaking |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m1980 |
| Contributing entity | University of Southern California |
| Rights | Vanovschi, Vitalii |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@dots.usc.edu |
| Filename | etd-Vanovschi-2613 |
| Archival file | uscthesesreloadpub_Volume32/etd-Vanovschi-2613.pdf |
Description
| Title | Page 1 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@dots.usc.edu |
| Full text | ELECTRONIC STRUCTURE AND SPECTROSCOPY IN THE GAS AND CONDENSED PHASE: METHODOLOGY AND APPLICATIONS. by Vitalii Vanovschi A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (CHEMISTRY) May 2009 Copyright 2009 Vitalii Vanovschi |
