Application of electronic structure calculations to vibrational spectroscopy and gas encapsulation in zeolites
Zeolites are an important class of aluminosilicate materials that have wide applications in heterogeneous catalysis, gas separations, and ion-exchange processes at industrial scales. The desire to continue doing research on zeolites and zeolitic materials continues to be strong for two reasons: (i) to discover new zeolites with unique framework structures and (ii) to modify existing zeolites to discover new functionalities for applications that utilize zeolites. These goals require extensive use of characterization techniques, which can be expensive and heavily reliant on conjecture or supposition. Thanks to the advancement of computational power as well as improved numerical algorithms, theoretical studies of zeolites have become a powerful and complementary tool in the zeolite science community over the last few decades. This dissertation uses computational techniques to aid in the characterization and analysis of zeolites. We first investigate the vibrational properties (i.e., infrared and Raman spectra) of sodalites, including sodalites that have been ion exchanged, by means of density functional theory (DFT) calculations. The resulting spectra serve as a reference for scientists (either experimentalists or theoreticians) in the zeolite community and guide future experimental efforts but might not be sensitive enough for quantitative measurements of ion-exchange levels. We then use DFT and the nudged elastic band method to investigate the rate of release of 85Kr from zeolites used to encapsulate radioactive krypton. Results from our theoretical analysis reveal that although zeolites should entrap 85Kr, they might not entrap the decay product, corrosive 85Rb. These findings lead to interpretations and conclusions that are diffcult if not impossible to acquire experimentally.