UC Merced

This dissertation has two main objectives. The first objective of this dissertation is to emphasize the importance of synergistic interactions between experimentalists and theorists. Such work can lead to a holistic understanding of chemical processes yielding an understanding whose whole is greater than the sum of its parts. Chapters two and three describe new insights on hydrolysis reactions at TiO2 and ZrO2 done in close collaboration with experimental colleagues. Studies of such metal oxides are motivated by the critical role they play in chemical catalysis and a multitude of other high-impact applications. As discussed in these two chapters, the rich spectroscopic data attained by experimentalists studying these systems can only be interpreted after engaging theoretical simulation. Interestingly, such calculations often stretch the capabilities of readily available computational models and often motivate new methodological and theoretical advancements to explore excited state computational methods.

Motivated by the titanium and zirconium studies, the second part of this dissertation evaluates a new tool for locating excited states at a ground state computational cost, which has been termed the Projection-based Maximum Overlap Method (PMOM) and Projection-based Initial Maximum Overlap Method (PIMOM). Chapter four introduces the PMOM and PIMOM methods and provides an initial demonstration of their applicability to various classes of excited electronic states. Chapter five extends the use of the model to the evaluation of excited state molecular properties, such as optimizing excited state minimum energy structures, evaluating adiabatic excitation energies, and calculating vibrational frequencies. Chapter six presents a case where PMOM and PIMOM successfully lead to simulations of the spectrum of methylene blue, while simulations using popular time-dependent density functional theory models seemingly fail to locate a spin-pure state. Chapter seven highlights the usage of PIMOM to explore exotic electronic excited states in Lanthanides. Specifically, this chapter discusses the photoelectron spectra of Gd2O-.

The final chapter reviews the results of the dissertation. Examining the outcomes of that work, the final chapter also outlines potential new directions motivated by the reported research.