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You searched for subject:(coupled clusters theory). Showing records 1 – 2 of 2 total matches.

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University of Southern California

1. Epifanovskiy, Evgeny. Development of predictive electronic structure methods and their application to atmospheric chemistry, combustion, and biologically relevant systems.

Degree: PhD, Chemistry, 2011, University of Southern California

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. Advisors/Committee Members: Krylov, Anna I. (Committee Chair), Wittig, Curt (Committee Member), Johnson, Clifford (Committee Member).

Subjects/Keywords: electronic structure theory; coupled clusters theory; equation of motion theory; organic chromophore; green fluorescent protein; uracil

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Epifanovskiy, E. (2011). Development of predictive electronic structure methods and their application to atmospheric chemistry, combustion, and biologically relevant systems. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/466781/rec/1963

Chicago Manual of Style (16th Edition):

Epifanovskiy, Evgeny. “Development of predictive electronic structure methods and their application to atmospheric chemistry, combustion, and biologically relevant systems.” 2011. Doctoral Dissertation, University of Southern California. Accessed October 15, 2019. http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/466781/rec/1963.

MLA Handbook (7th Edition):

Epifanovskiy, Evgeny. “Development of predictive electronic structure methods and their application to atmospheric chemistry, combustion, and biologically relevant systems.” 2011. Web. 15 Oct 2019.

Vancouver:

Epifanovskiy E. Development of predictive electronic structure methods and their application to atmospheric chemistry, combustion, and biologically relevant systems. [Internet] [Doctoral dissertation]. University of Southern California; 2011. [cited 2019 Oct 15]. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/466781/rec/1963.

Council of Science Editors:

Epifanovskiy E. Development of predictive electronic structure methods and their application to atmospheric chemistry, combustion, and biologically relevant systems. [Doctoral Dissertation]. University of Southern California; 2011. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/466781/rec/1963


University of Southern California

2. Vanovschi, Vitalii. Electronic structure and spectroscopy in the gas and condensed phase: methodology and applications.

Degree: PhD, Chemistry, 2011, University of Southern California

Method developments and applications of the condensed phase and gas phase modeling techniques are presented in two parts of this work.; In the first part, the theory of the effective fragment potential (EFP) method designed for accurate modeling of the molecular properties of the extended systems is introduced. The implementation of EFP developed in this work within the Q-Chem electronic structure package is discussed in details. The code is applied to the studies of Pi - Pi interactions in benzene oligomers. The primary interest of these studies are the many-body and total non-additive Pi - Pi interactions. A detailed comparison of EFP with ab initio theories is presented for the set of eight benzene trimers. Three-body intermolecular interaction energies at the EFP level of theory are within 0.04 kcal/mol from the full ab initio results. To elucidate the asymptomatic behavior of the total non-additive binding energy, three types of linear benzene oligomers with 10, 20, 30 and 40 monomers are modeled using our new EFP implementation. The result of this investigation is that with the increase in the size of linear benzene clusters, the share of the total non-binding energy approaches a constant and does not exceed 4% for the structures considered in the study. This result indicates that there are no substantial non-local effects in the binding mechanism of linear benzene clusters.; In the second part, the equilibrium structure, vibrational frequencies, and ionization energies of the para-benzyne radical anion are characterized by coupled-cluster and equation-of-motion methods. Vibronic interactions with the low-lying excited state result in a flat potential energy surface along the coupling mode and even in lowersymmetry C2v structures. Additional complications arise due to the Hartree-Fock instabilities and near-instabilities. The magnitude of vibronic interactions was characterized by geometrical parameters, charge localization patterns and energy differences between the D2h and C2v structures. The observed trends suggest that the C2v minimum predicted by several theoretical methods is an artifact of an incomplete correlation treatment. The comparison between the calculated and experimental spectrum confirmed D2h structure of the anion, as well as accuracy of the coupled-cluster and spin-flip geometries, frequencies and normal modes of the anion and the diradical. Density functional calculations (B3LYP) yielded only a D2h minimum, however, the quality of the structure and vibrational frequencies is poor, as follows from the comparison to the high-level wave function calculations and the calculated spectrum. The analysis of charge localization patterns and the performance of different functionals revealed that B3LYP underestimates the magnitude of vibronic interactions due to self-interaction error. Advisors/Committee Members: Krylov, Anna I. (Committee Chair), Wittig, Curt (Committee Member), Haas, Stephan (Committee Member).

Subjects/Keywords: effective fragment potential; benzene clusters; para-benzyne radical anion; photoelectron spectroscopy; coupled-cluster methods; density functional theory; symmetry breaking

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Vanovschi, V. (2011). Electronic structure and spectroscopy in the gas and condensed phase: methodology and applications. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/147045/rec/2277

Chicago Manual of Style (16th Edition):

Vanovschi, Vitalii. “Electronic structure and spectroscopy in the gas and condensed phase: methodology and applications.” 2011. Doctoral Dissertation, University of Southern California. Accessed October 15, 2019. http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/147045/rec/2277.

MLA Handbook (7th Edition):

Vanovschi, Vitalii. “Electronic structure and spectroscopy in the gas and condensed phase: methodology and applications.” 2011. Web. 15 Oct 2019.

Vancouver:

Vanovschi V. Electronic structure and spectroscopy in the gas and condensed phase: methodology and applications. [Internet] [Doctoral dissertation]. University of Southern California; 2011. [cited 2019 Oct 15]. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/147045/rec/2277.

Council of Science Editors:

Vanovschi V. Electronic structure and spectroscopy in the gas and condensed phase: methodology and applications. [Doctoral Dissertation]. University of Southern California; 2011. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/147045/rec/2277

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