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Time-Dependent Density-Functional Description of the 1La State in Polycyclic Aromatic Hydrocarbons

Richard, Ryan M.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1302098974

Abstract Details

2011, Master of Science, Ohio State University, Chemistry.
The electronic spectrum of alternant polycyclic aromatic hydrocarbons (PAHs) includes two singlet excited states that are often denoted 1La and 1Lb. Time-dependent density functional theory (TD-DFT) afford reasonable excitation energies for the 1Lb state in such molecules, but often severely underestimates 1La excitation energies, and fails to reproduce observed trends in the 1La excitation energy as a function of molecular size. Here, we examine the performance of long-range-corrected (LRC) density functionals for the 1La and 1Lb states of various PAHs. With an appropriate choice for the Coulomb attenuation parameter, we find that LRC functionals avoid the severe underestimation of the 1La excitation energies that afflicts other TD-DFT approaches, while errors in the 1Lb excitation energies are less sensitive to this parameter. This suggests that the 1La states of certain PAHs exhibit some sort of charge-separated character, consistent with the description of this state within valence-bond theory, but such character proves difficult to identify a priori. We conclude that TD-DFT calculations in medium-size, conjugated organic molecules may involve significant but hard-to-detect errors. Comparison of LRC and non-LRC results is recommended as a qualitative diagnostic.
John M. Herbert, PhD (Advisor)
Sherwin J. Singer, PhD (Committee Member)
72 p.
Physical Chemistry
Time-Dependent Density Functional Theory; Polycyclic Aromatic Hydrocarbons

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Citations

  • Richard, R. M. (2011). Time-Dependent Density-Functional Description of the 1La State in Polycyclic Aromatic Hydrocarbons [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1302098974

    APA Style (7th edition)

  • Richard, Ryan. Time-Dependent Density-Functional Description of the 1La State in Polycyclic Aromatic Hydrocarbons. 2011. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1302098974.

    MLA Style (8th edition)

  • Richard, Ryan. "Time-Dependent Density-Functional Description of the 1La State in Polycyclic Aromatic Hydrocarbons." Master's thesis, Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1302098974

    Chicago Manual of Style (17th edition)

osu1302098974
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© 2011, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.