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Figure 5.7: Relative energies of the 1Ag and 3B1u states of para-benzyne diradical at
their equilibrium structures and MECP. Both at the singlet and triplet equilibrium
geometry, the singlet is below the triplet. The two states intersect 0.65 eV above the
ground state minimum.
The MECP was located 0.65 eV above the ground state equilibrium energy as shown
in the energy diagram in Fig. 5.7. The nuclear configuration at this point is significantly
distorted compared to the ground state geometry. Note that although this distortion
increases the splitting between the frontier MOs due to increased through-space interac-tion
between the radical centers, it stabilizes the ag orbital, due to the favorable through-bond
interactions45.
5.5 Discussion: Performance of the algorithm and
details of implementation
Our implementation of the projected gradient algorithm employs the minimization tech-nique
used in Q-Chem: the Newton-Raphson method in conjunction with the eigenvalue
following algorithm46. An approximate guess Hessian matrix used for the optimization
153
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 163 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | Figure 5.7: Relative energies of the 1Ag and 3B1u states of para-benzyne diradical at their equilibrium structures and MECP. Both at the singlet and triplet equilibrium geometry, the singlet is below the triplet. The two states intersect 0.65 eV above the ground state minimum. The MECP was located 0.65 eV above the ground state equilibrium energy as shown in the energy diagram in Fig. 5.7. The nuclear configuration at this point is significantly distorted compared to the ground state geometry. Note that although this distortion increases the splitting between the frontier MOs due to increased through-space interac-tion between the radical centers, it stabilizes the ag orbital, due to the favorable through-bond interactions45. 5.5 Discussion: Performance of the algorithm and details of implementation Our implementation of the projected gradient algorithm employs the minimization tech-nique used in Q-Chem: the Newton-Raphson method in conjunction with the eigenvalue following algorithm46. An approximate guess Hessian matrix used for the optimization 153 |
