Date of Award
2017
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Graduate Group
Chemistry
First Advisor
Joseph E. Subotnik
Abstract
Photochemical reactions, which involve both the ground and excited electronic states of
a molecule, can promote processes otherwise inaccessible by normal reactions. In general,
photochemical reactions may be classified as adiabatic or nonadiabatic depending on
whether the reaction takes place on the same adiabatic potential energy surface or not.
From research over the last two decades, we now understand that many processes in nature
turn out to be nonadiabatic { including charge transfer, electronic excitation quenching,
and spin-forbidden transitions. The efficiency of such processes depends critically on the
electron-nuclear interaction, which is quantified by the derivative coupling between the two
involved states.
The first part of the work (chapters 3-6) presented here mainly focuses on understanding
the electron-nuclear interaction using the electronic structure theory. Two approaches
are developed calculating the derivative couplings between the excited states within the
time-dependent density functional theory. The behavior of the derivative couplings around
a conical intersection is analyzed for two real molecules: benzaldehyde and protonated
formaldamine.
The second part of this work (chapters 7-8) focuses on understanding the electron-electron
interaction in the framework of Green's function. Detailed working equations are derived
for the GW approximation, which is used to calculate the electron attachment/detachment
energy, and the Bethe-Salpeter equation, which is used to obtain the electron excitation
energies of a system.
Recommended Citation
Ou, Qi, "Tddft Derivative Couplings And Other Topics In Quantum Chemistry" (2017). Publicly Accessible Penn Dissertations. 2509.
https://repository.upenn.edu/edissertations/2509