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Figure 5.2: D3h-constrained scans of adiabatic PESs of N+3
around the points of
intersections calculated by EOM-CCSD/6-31G.
When the molecule is constrained to the C2v point group symmetry, the spacial parts
of the wavefunctions of the states belong to different irreps, A1 and B2, and the derivative
coupling matrix element between them vanishes.
If the symmetry is lowered further to the Cs point group symmetry, and the N–O
bond lengths are allowed to vary independently, both the ground state and first excited
state wavefunctions become of the A0 symmetry. The derivative coupling matrix element
between the two states is no longer zero, and the intersection becomes truly conical.
The calculations were performed using the EOMIP-CCSD method. The closed-shell
CCSD wavefunction for NO2
was used as the reference for the EOM-IP calculations.
To locate and minimize the seam numerically, the two surfaces were first scanned.
The N–O distance was varied from 1.20 °A
to 1.40 A° , and at each point the O–N–O
angle was varied from 90 to 130 , as shown in Fig. 5.3. These results are summarized
in Table 5.3. The minimum of the seam was located at R(NO) = 1:3045 A° , a(ONO) =
106:75 .
147
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 157 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | Figure 5.2: D3h-constrained scans of adiabatic PESs of N+3 around the points of intersections calculated by EOM-CCSD/6-31G. When the molecule is constrained to the C2v point group symmetry, the spacial parts of the wavefunctions of the states belong to different irreps, A1 and B2, and the derivative coupling matrix element between them vanishes. If the symmetry is lowered further to the Cs point group symmetry, and the N–O bond lengths are allowed to vary independently, both the ground state and first excited state wavefunctions become of the A0 symmetry. The derivative coupling matrix element between the two states is no longer zero, and the intersection becomes truly conical. The calculations were performed using the EOMIP-CCSD method. The closed-shell CCSD wavefunction for NO2 was used as the reference for the EOM-IP calculations. To locate and minimize the seam numerically, the two surfaces were first scanned. The N–O distance was varied from 1.20 °A to 1.40 A° , and at each point the O–N–O angle was varied from 90 to 130 , as shown in Fig. 5.3. These results are summarized in Table 5.3. The minimum of the seam was located at R(NO) = 1:3045 A° , a(ONO) = 106:75 . 147 |
