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ELECTRONIC STRUCTURE OF IONIZED NON-COVALENT DIMERS:
METHODS DEVELOPMENT AND APPLICATIONS
by
Anna A. Golubeva
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMISTRY)
May 2010
Copyright 2010 Anna A. Golubeva
Object Description
| Title | Electronic structure of ionized non-covalent dimers: methods development and applications |
| Author | Golubeva, Anna A. |
| Author email | golubeva@usc.edu; ane4ka.golubeva@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemistry |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2009-11-17 |
| Date submitted | 2010 |
| Restricted until | Unrestricted |
| Date published | 2010-04-05 |
| Advisor (committee chair) | Krylov, Anna I. |
| Advisor (committee member) |
Mak, Chi Ho Haas, Stephan |
| Abstract | Several prototypical ionized non-covalent dimers - the uracil, 1,3-dimethylated uracil and benzene dimer cations - are studied by high-level ab initio approaches including the equation-of-motion coupled cluster method for ionization potentials (EOM-IP-CC). The qualitative Dimer Molecular Orbitals as Linear Combinations of Fragment Molecular Orbitals (DMO-LCFMO) framework is used to interpret the results of calculations. As the simplest model systems, the neutral and ionized non-covalent dimers, such as pi-stacked and H-bonded nucleobase dimers, can shed some light on the complex mechanism of the charge transfer in DNA. The correct treatment of non-covalent interactions is challenging to the ab initio methodology, therefore the special attention is given to the development and benchmarking of the new methods.; First, we introduce and benchmark the cost-saving configuration-interaction variant of the EOM-IP-CCSD method: EOM-IP-CISD. The computational scalling of EOMIP-CISD in N5, as opposed to the N6 scalling of EOM-IP-CCSD. The EOM-IP-CISD structures for the open-shell systems are of a similar quality as the HF geometries of well-behaved closed-shell molecules, while the excitation energies are of a semiquantitative value. The performance of promising Density Functional Theory developments, i.e. the novel long-range and dispersion-corrected functionals, is also assessed throughout this work.; Next, the potential energy surfaces, electronic structure and properties of uracil dimer and 1,3-dimethylated uracil dimer cations are investigated. The electronic structure of dimers is explained by DMO-LCFMO. Non-covalent interactions lower the vertical ionization energies by up to 0.35 eV, the largest red-shift is observed for the stacked and t-shaped structures. Ionization induces significant changes in bonding patterns, structures and binding energies. In the cations the interaction between the fragments becomes more covalent and the binding energies are 1.5-2.0 times larger than in the neutrals. The relaxation of the cation structures is governed by two different mechanisms: the hole delocalization and the electrostatic stabilization. The electronic spectra of dimer cations exhibit significant changes upon relaxation, which can be exploited to experimentally monitor the ionization-induced dynamics. The position and intensity of the charge-resonance transitions can be used as spectroscopic probes in such experiments. Finally, we investigate the effect of substituents on the electronic structure of non-covalent dimers. For weak perturbations, i.e. the CH3 group, the effect of substituents can be incorporated into the qualitative DMO-LCFMO picture as constant shifts of the dimers and the monomers levels.; Future research topics, such as the conical intersections in the benzene dimer cations and the electronic structure of the chemically-modified nucleobase dimers, are discussed in the last chapter. |
| Keyword | ionized dimers; non-covalent dimers; nucleobase dimers; uracil dimer; methylated uracil dimer; benzene dimer; equation-of-motion method; EOM-IP; EOM-IP-CC; EOM-IP-CISD; effect of substituents; electronic structure; electronic spectrum of dimer cation |
| 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-m2878 |
| Contributing entity | University of Southern California |
| Rights | Golubeva, Anna A. |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Golubeva-3405 |
| Archival file | uscthesesreloadpub_Volume40/etd-Golubeva-3405.pdf |
Description
| Title | Page 1 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | ELECTRONIC STRUCTURE OF IONIZED NON-COVALENT DIMERS: METHODS DEVELOPMENT AND APPLICATIONS by Anna A. Golubeva A Dissertation Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (CHEMISTRY) May 2010 Copyright 2010 Anna A. Golubeva |
