UC Berkeley

This thesis is concerned with the application, development, and assessment of computational approaches to treat chemical reactions from an electronic structure theory perspective. In Chapter 2, the recently developed density functional, wB97X-V, and coupled cluster with single, double and perturbative triple excitations [CCSD(T)] are applied to study the reaction networks of excited state silicon atoms with allene and methylacetylene in the circumstellar envelope of carbon stars. In Chapter 3, another recently developed density functional, wB97M-V, and CCSD(T) are used to benchmark the performance of the ReaxFF reactive force field as applied to hydrogen combustion systems. In Chapter 4, an extension of third-order Moller-Plesset perturbation theory (MP3) and regularized perturbation theory (k-OOMP2) is developed and used to calculate thermochemistry, barrier heights, and noncovalent interaction energies. In Chapter 5, the use of k-OOMP2 optimized orbitals is extended to CCSD(T) and used to investigate the vibrational frequencies of diatomic molecules.