UC Davis

Computational chemistry is an expansive field that is able to answer many different questions. However, inorder to answer any given problem a unique set of tools must be used. In this work, a variety of computational techniques was employed to tackle a diverse set of fundamental science questions. These methods included ab initio molecular dynamics, free energy dynamics, density functional theory, and multi-reference configuration interaction. Reaction discovery oriented tools were used to develop a mechanism for the oligomerization of red phosphorus from the ground up. This happens primarily via diphosphorus additions at π-bonds and weak σ-bonds through three-membered ring intermediates. Downhill paths through P6 and P8 clusters eventually result in P10 clusters that can oligomerize into red phosphorus chains. The initial, rate limiting step for this process has an energy barrier of 24.2 kcal/mol.

In addition to reaction characterization tools, computational techniques were use to find electron param-agnetic resonance spectroscopic values for species involved in the oligomerization of DABCO via radical oxidation. Computational tools lent insight that an initial proposed theory of a localized carbon radical forming by an initial cracking of C-C σ-bonds is likely not plausible, and that σ-bond cleavage happens si- multaneously with dimerization. Lastly, multi-configuration methods were used to do preliminary studies on the photodissociation of the CH molecule, which is abundant in space and may be used to track astronomical phenomena. A large dissociative Π state seems to intersect the other Rydberg Π states of CH, which will likely be a significant feature in the photodissociation of CH. Up to thirteen excited 2Π states were able to be characterized in the valence region. Looking forward, improved reference wavefunctions will be needed to better characterize the dissociative region.