Applications of quantum chemistry to gas and solid phase reaction kinetics

Chemical kinetics has nourished from the achievements of computational quantum chemistry as perhaps no other field. This thesis illustrates the application of first-principles calculations to elucidate complex reaction mechanisms, and to quantitatively simulate reaction rates. The work embodied in this dissertation encompasses several projects with very diverse applications. In some cases, quantum chemistry calculations have been used for predicting reaction rates, while in others they are used in a semi-qualitative manner to elucidate complex reaction mechanisms.; The first two chapters of this dissertation explain some key theoretical concepts of quantum chemistry and chemical kinetics. They are not intended to be exhaustive or detailed, but rather to illustrate general principles that are applied in the subsequent chapters. Chapter three reviews the disperse literature on the statistical treatment of internal rotors and provides a comparison of commonly used approximations.; Chapters four through six cover three areas of special interest to gas-phase kinetics: bond dissociation energies, transition state theory and unimolecular reactions, with particular emphasis on combustion and atmospheric chemistry applications. A critical assessment of reaction barriers and bond dissociation energies calculated with several ab initio methods in common use is provided in chapters four and five, respectively.; Chapters seven and eight illustrate how quantum chemistry can be used to decipher complex reaction mechanisms, with applications to current and future problems in semiconductor processing. The former studies the mechanisms of boron diffusion through thin gate oxide layers in metal oxide field effect transistors (MOSFETs). The latter investigates the details of atomic layer deposition (ALD) reactions on germanium and silicon-germanium alloys. Both of these studies are motivated by the miniaturization trend in gate oxide layers in MOSFET devices. As the device feature size is scaled down, a lower operating voltage must be applied to maintain a constant electrical field, thereby requiring a larger capacitance. The capacitance can be increased by reducing the oxide thickness (as has been happening so far) or by substituting silica in transistor gates with a new material with a higher dielectric constant.