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CIS(D). The accuracy of SOS-CIS(D) is very similar to that of CIS(D) for valence
states, whereas the performance for the Rydberg states is improved. Based on a set of
over forty various excited states in over twenty organic molecules, the mean signed error
in the SOS-CIS(D) vertical excitation energy is 0.02 eV for valence states and 0.08 eV
for Rydberg transitions. Limitations of SOS-MP2 and SOS-CIS(D) are the same as MP2
and CIS(D), respectively. For example, these methods fail when the ground-state wave
function acquires a significant multiconfigurational character, as at a cis-trans isomer-ization
transition state, and for excited states with considerable doubly excited character.
Open-shell (e.g., doublet) states can also cause difficulties due to spin-contamination.
1.1.3 Density functional theory methods
Long-range-corrected density functionals
In long-range-corrected functionals, a range-separated representation of the Coulomb
operator80, 81 is used to mitigate the effects of the self-interaction error. The contribution
from the short-range part is described by a local functional, whereas the long-range part
is described using the exact Hartree-Fock exchange. The separation depends on a param-eter
g. In the BNL approach82, g is optimized for each system using Koopmans-like argu-ments:
g is adjusted such that the HOMO energy equals the difference between the total
BNL energies of the N- and N-electron systems. Initial benchmarks82, 83 demonstrated
an encouraging performance for excited states, and even such challenging systems as
ionized dimers. In wPB97X84, g and other parameters are optimized using standard
training sets. Benchmark results have demonstrated consistently improved performance
relative to non-long-range-corrected functionals.
18
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 28 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | CIS(D). The accuracy of SOS-CIS(D) is very similar to that of CIS(D) for valence states, whereas the performance for the Rydberg states is improved. Based on a set of over forty various excited states in over twenty organic molecules, the mean signed error in the SOS-CIS(D) vertical excitation energy is 0.02 eV for valence states and 0.08 eV for Rydberg transitions. Limitations of SOS-MP2 and SOS-CIS(D) are the same as MP2 and CIS(D), respectively. For example, these methods fail when the ground-state wave function acquires a significant multiconfigurational character, as at a cis-trans isomer-ization transition state, and for excited states with considerable doubly excited character. Open-shell (e.g., doublet) states can also cause difficulties due to spin-contamination. 1.1.3 Density functional theory methods Long-range-corrected density functionals In long-range-corrected functionals, a range-separated representation of the Coulomb operator80, 81 is used to mitigate the effects of the self-interaction error. The contribution from the short-range part is described by a local functional, whereas the long-range part is described using the exact Hartree-Fock exchange. The separation depends on a param-eter g. In the BNL approach82, g is optimized for each system using Koopmans-like argu-ments: g is adjusted such that the HOMO energy equals the difference between the total BNL energies of the N- and N-electron systems. Initial benchmarks82, 83 demonstrated an encouraging performance for excited states, and even such challenging systems as ionized dimers. In wPB97X84, g and other parameters are optimized using standard training sets. Benchmark results have demonstrated consistently improved performance relative to non-long-range-corrected functionals. 18 |
