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configuration. Electronic states with the smallest value of energy Ei are called ground
electronic states. States with the same value of energy are called degenerate states. It
is possible to have degenerate ground electronic states, however in this work we are
mainly concerned with the class of systems that have only one ground electronic state.
Each electronic wave function Yi belongs to one of the irreducible representations
of the molecule’s point group symmetry. The corresponding state is labeled with that
irrep, which is called the “state symmetry.” In addition, each wave function Yi is an
eigenfunction of the spin-squared operator S2, and the respective eigenvalue is the “state
spin” or “state multiplicity.” States of the same symmetry and spin form manifolds that
are uncoupled from each other. This makes it possible to solve Eq. 1.2 with appropriate
constraints for each irrep and multiplicity independently.
Let us introduce an order of the electronic states by their energies such that
Ei Ej 8i; j : i < j (1.3)
Then (E0;Y0) is the ground state.
Solving the electronic Schr¨odinger equation at every nuclear configuration R 2 R3N
(N is the number of atoms, and 3N is the total number of three-dimensional Cartesian
coordinates) and then ordering the solutions as prescribed by Eq. 1.3 allows us to define
functions Vi : R3N ! R that yield the energy of i-th state at the given positions of the
nuclei R
EijR =Vi(R) (1.4)
The function Vi(R) is called the adiabatic potential energy surface (PES) of i-th elec-tronic
state. Examples are shown in Fig. 1.1 (Reproduced from Ref. 2).
2
Object Description
| Title | Development of predictive electronic structure methods and their application to atmospheric chemistry, combustion, and biologically relevant systems |
| Author | Epifanovskiy, Evgeny |
| Author email | epifanov@usc.edu; epifanov@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemistry |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2011-03-21 |
| Date submitted | 2011 |
| Restricted until | Unrestricted |
| Date published | 2011-04-28 |
| Advisor (committee chair) | Krylov, Anna I. |
| Advisor (committee member) |
Wittig, Curt Johnson, Clifford |
| Abstract | This work demonstrates electronic structure techniques that enable predictive modeling of the properties of biologically relevant species. Chapters 2 and 3 present studies of the electronically excited and detached states of the chromophore of the green fluorescent protein, the mechanism of its cis-trans isomerization, and the effect of oxidation. The bright excited ππ∗ state of the chromophore in the gas phase located at 2.6 eV is found to have an autoionizing resonance nature as it lies above the electron detachment level at 2.4 eV. The calculation of the barrier for the ground-state cis-trans isomerization of the chromophore yields 14.8 kcal/mol, which agrees with an experimental value of 15.4 kcal/mol; the electronic correlation and solvent stabilization are shown to have an important effect. In Chapter 3, a one-photon two-electron mechanism is proposed to explain the experimentally observed oxidative reddening of the chromophore. Chapter 4 considers the excited states of uracil. It demonstrates the role of the one-electron basis set and triples excitations in obtaining the converged values of the excitation energies of the nπ∗ and ππ∗ states. The effects of the solvent and protein environment are included in some of the models.; Chapter 5 describes an implementation of the algorithm for locating and exploring intersection seams between potential energy surfaces. The theory is illustrated with examples from atmospheric and combustion chemistry. |
| Keyword | electronic structure theory; coupled clusters theory; equation of motion theory; organic chromophore; green fluorescent protein; uracil |
| 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-m3801 |
| Contributing entity | University of Southern California |
| Rights | Epifanovskiy, Evgeny |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Epifanovskiy-4557 |
| Archival file | uscthesesreloadpub_Volume14/etd-Epifanovskiy-4557.pdf |
Description
| Title | Page 12 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | configuration. Electronic states with the smallest value of energy Ei are called ground electronic states. States with the same value of energy are called degenerate states. It is possible to have degenerate ground electronic states, however in this work we are mainly concerned with the class of systems that have only one ground electronic state. Each electronic wave function Yi belongs to one of the irreducible representations of the molecule’s point group symmetry. The corresponding state is labeled with that irrep, which is called the “state symmetry.” In addition, each wave function Yi is an eigenfunction of the spin-squared operator S2, and the respective eigenvalue is the “state spin” or “state multiplicity.” States of the same symmetry and spin form manifolds that are uncoupled from each other. This makes it possible to solve Eq. 1.2 with appropriate constraints for each irrep and multiplicity independently. Let us introduce an order of the electronic states by their energies such that Ei Ej 8i; j : i < j (1.3) Then (E0;Y0) is the ground state. Solving the electronic Schr¨odinger equation at every nuclear configuration R 2 R3N (N is the number of atoms, and 3N is the total number of three-dimensional Cartesian coordinates) and then ordering the solutions as prescribed by Eq. 1.3 allows us to define functions Vi : R3N ! R that yield the energy of i-th state at the given positions of the nuclei R EijR =Vi(R) (1.4) The function Vi(R) is called the adiabatic potential energy surface (PES) of i-th elec-tronic state. Examples are shown in Fig. 1.1 (Reproduced from Ref. 2). 2 |
