UC Berkeley

Molecular properties act as the interface between electronic structure theory and experimental chemistry. Several recently developed electronic structure methods have proved to produce accurate electronic energies in an efficient manner, but their applications to molecular properties calculations remain under-developed. This thesis explores the application of accurate and efficient electronic structure methods for energy calculations to the calculation of molecular properties. In Chapter 2, a method independent, fully numerical finite difference approach to calculating molecular magnetic properties is presented. Two recently proposed methods, regularized second-order Møller-Plesset perturbation theory (κ-MP2) and variants of the third-order Møller-Plesset perturbation theory (MP3) are used to calculate nuclear magnetic resonance chemical shifts. The scaled MP3 method, MP2.X, is found to be the best performing among the methods inspected: it produces lower errors for heavy nuclei than coupled cluster with singles and doubles (CCSD), a method with the same cost scaling and higher prefactor. In particular, MP2.5 produced an impressive two-fold improvement over CCSD for 13C shieldings, while MP2.6 produced an extraordinary six-fold improvement over CCSD for 15N shieldings. The simpler and cheaper κ-MP2, with weak regularization, had smaller errors for 13C shieldings than CCSD as well. In Chapter 3, analytic nuclear gradients for the regularized orbital optimized second-order M{\o}ller-Plesset perturbation theory (κ-OOMP2) is developed. It was then applied to several interesting chemical problems, including radical geometry and vibrational frequencies, chalcogen bonding, and singlet-triplet gaps. κ-OOMP2 was able to resolve most of the artifacts stemming from HF orbitals. Compared to the regularization strength suitable for thermochemistry, weaker regularization is more suitable for the problems examined in this work. Finally, Chapter 4 presents a mechanistic study of solvent oxygen incorporation into the products of CO reduction on Cu using a recently developed density functional ωB97M-V. This work found that isotopic scrambling of carbonyl-containing intermediate reaction products that are reduced further to oxygenated products provides a simple explanation to the observed solvent oxygen incorporation.