Solid state NMR and atomistic molecular dynamics simulation study of ionic conductors, catalysts and perovskites

High-resolution magic angle spinning (MAS) NMR of the solid state and its variants have been instrumental in providing detailed structural information in solids. It is also a very important spectroscopic method for understanding ionic motions in solids. This powerful technique complements information available from crystallography. Molecular dynamics simulation, on the other hand, is a useful technique for modeling interactions in solids and investigating dynamics in the time scale of picoseconds to milliseconds. The work presented in this dissertation, combines these methods to provide an atomic level description of dynamic processes that control many important structural and functional properties of materials.; The layered anionic conductor family based on PbSnF₄ structure is a record holder in anionic conduction. Hence, these materials are potential candidates for room temperature solid-electrolyte in fuel cell applications and in development of solid-state temperature solid-electrolyte in fuel cell applications and in development of solid-state sensors. One member of this family, BaSnF₄, has been studied using high-resolution solid-state NMR techniques, to understand the origin of ionic conduction. MD simulation results on this ionic conductor proved useful in understanding the origin of superionicity and also provided insights on improving overall conductivity. Solid-state NMR has also been used to look at model perovskite systems. A solid solution of NaMgF₃ and KMgF₃ has been studied to understand effects of cation doping on phase transition and other mesoscopic properties in this solid.; Simulation results presented in this thesis use a polarizable description of atoms in a classical molecular dynamics framework, to look at catalytically active disordered materials. A potential model based on polarizable ion model (PIM), has been developed to study phase transitions and catalytic activities in a commercial halogen exchange catalyst, α-AlF₃, in bulk and nanophase. The MD simulations on this model illustrate the role of dynamic processes in structural phase transition and the origin of catalytic activity due to finite size effects in nanoscale. The results were confirmed with available experimental NMR and crystallographic data.; Inputs from MD simulations can in turn be used for arriving at better crystallographic refinement models, designing synthetic routes and studying ways of improving catalytic activity in high surface-area materials. This approach can serve as an effective paradigm for integrating experimental structural-characterization methods like solid-state NMR and crystallography, with theoretical modeling and simulations. Such an approach can be invaluable for computer-aided design of inorganic materials.