The development of the semi-empirical atomistic potential called the embedded atom method (EAM) has allowed for the efficient modeling of solid-state environments, at a lower computational cost than afforded by density functional theory (DFT). This offers the capability of EAM to model the energetics of solid-state phases of varying coordination, including defects, such as vacancies and self-interstitials. This dissertation highlights the development and application of two EAMs: a Ti potential constructed with the multi-state modified embedded atom method (MS-MEAM), and a Ni potential constructed with the fragment Hamiltonian (FH) method. Both potentials exhibit flexibility in the description of different solid-states phases and applications. This dissertation also outlines two applications of DFT. First, a study of structure and stability for solid-state forms of NixCy (in which x and y are integers) is investigated using plane-wave DFT. A ground state phase for Ni2C is elucidated and compared to known and hypothesized forms of NixCy. Also, a set of correlation consistent basis sets, previously constructed using the B3LYP and BLYP density functionals, are studied. They are compared to the well-known to the correlation consistent basis sets that were constructed with higher-level ab initio methodologies through computations of enthalpies of formation and combustion enthalpies. …

The reactions of atomic hydrogen with methanethiol and that of atomic hydrogen with carbon disulfide were studied experimentally using flash-photolysis resonance-fluorescence techniques. Rate constants were determined over a range of temperatures and pressures, and through analysis and comparison to theoretical work details of the reactions were ascertained.