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Ab-Initio Implementation of Ground and Excited State Resonance Raman Spectroscopy: Application to Condensed Phase and Progress Towards Biomolecules

Dasgupta, Saswata
http://rave.ohiolink.edu/etdc/view?acc_num=osu1591053672243115

Abstract Details

2020, Doctor of Philosophy, Ohio State University, Chemistry.
We discuss the development and application of multiple methodologies which will either make the traditional electronic structure methods more efficient or reveal the structural insight of condensed or gas-phase systems. The main idea revolves around the development and application of \textit{ab initio} resonance-Raman (RR) spectroscopy and how to achieve the efficiency to simulate the resonance-Raman spectra for biomolecules. To tackle this, the first step was the development of new quadrature grids for high precision integration of modern density functionals, as the choice of density functional for RR simulation stems from the former's accuracy and cost-effectiveness. Our pruned integration grids, SG-2 and SG-3 work well for modern difficult-to-integrate functionals alongside finding a balance between accuracy and computational cost. To calculate the vibrational spectra for a biomolecule, getting the optimized structure is important as normal mode analysis can be erroneous at a non-stationary point. All quantum-mechanical optimization of enzyme active sites can be tricky geometric constraints that need to be introduced to prevent the structural collapse of the model system during geometry optimizations that do not contain a full protein backbone. We introduce a simple alternative in which terminal atoms of the model system are placed in soft harmonic confining potentials rather than being rigidly constrained. The new approach is more efficient for optimizing minima and transition states, as compared to the use of fixed-atom constraints, and also more robust against unwanted imaginary frequencies. To calculate the RR intensities using all-electron quantum chemistry, we used the excited state gradient method under the independent mode displaced harmonic oscillator (IMDHO) approximation. Using the RR spectroscopy we get insightful information about the structure of the hydrated electron, which caused a decade long debate. Furthermore, we have integrated the \textit{ab-initio} molecular dynamics (AIMD) simulation of excited states along with the resonance Raman calculation to substantiate the experimental femtosecond stimulated Raman spectra (FSRS) spectra. This formalism helps us to understand the time-dependent evolution of specific vibrational modes.
John Herbert, Dr. (Advisor)
Alexander Sokolov, Dr. (Committee Member)
Hannah Shafaat, Dr. (Committee Member)
205 p.
Chemistry; Physical Chemistry
Electronic Structure Theory; Quantum Chemistry; Resonance-Raman Spectroscopy; Density Functional Theory; Enzymatic reactions; Femtosecond stimulated Raman spectroscopy

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Citations

  • Dasgupta, S. (2020). Ab-Initio Implementation of Ground and Excited State Resonance Raman Spectroscopy: Application to Condensed Phase and Progress Towards Biomolecules [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1591053672243115

    APA Style (7th edition)

  • Dasgupta, Saswata. Ab-Initio Implementation of Ground and Excited State Resonance Raman Spectroscopy: Application to Condensed Phase and Progress Towards Biomolecules. 2020. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1591053672243115.

    MLA Style (8th edition)

  • Dasgupta, Saswata. "Ab-Initio Implementation of Ground and Excited State Resonance Raman Spectroscopy: Application to Condensed Phase and Progress Towards Biomolecules." Doctoral dissertation, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1591053672243115

    Chicago Manual of Style (17th edition)

osu1591053672243115
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