
Electronic Theses and Dissertations
Date
2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Chemistry
Committee Chair
Daniel Nascimento
Committee Member
Nathan DeYonker
Committee Member
Qianyi Cheng
Committee Member
Xiao Shen
Committee Member
Yongmei Wang
Abstract
This dissertation addresses the challenges in simulating the core-level spectra of transition metal complexes, focusing on validating simplified methods that are both efficient and sufficiently accurate. Proper simulation requires incorporating relativistic effects, such as spin-orbit coupling, which significantly increases computational demands. To address these difficulties, this work provides an overview of the theoretical foundations behind the employed methodologies, including linear-response time-dependent density functional theory (LR-TD-DFT) and the zeroth-order regular approximation (ZORA) Hamiltonian, and the state-interaction framework. Key findings demonstrate that simplified state-interaction-based approaches produce near-edge X-ray absorption spectra (XAS) that are nearly indistinguishable from those obtained using more rigorous methods, ensuring reliable analysis at a fraction of the computational cost. Further optimization can be achieved by applying approximations to the $\sigma$ vectors in the Davidson algorithm, which are constructed from the Fock matrix, Coulomb and exchange-like terms, and the exchange-correlation kernel. Our studies have revealed that the exchange-correlation kernel has a negligible impact on the qualitative features of the spectra, whereas the Hartree-Fock exchange term is crucial. These results establish the validity of the simplified approaches, highlighting their potential to reduce computational overhead without compromising accuracy.
Library Comment
Notes
Open access.
Recommended Citation
Pak, Sarah, "Approximate Time-Dependent Density Functional Theory Methods for Simulating X-ray Absorption Spectra in Transition Metal Complexes" (2025). Electronic Theses and Dissertations. 3765.
https://digitalcommons.memphis.edu/etd/3765
Comments
Data is provided by the student.