Huertas Miranda, Javier A.

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    Molecular simulation studies for the templated synthesis of ultrathin metal nanowires in zeolites
    (2012) Huertas Miranda, Javier A.; Martínez Iñesta, María M.; College of Engineering; Hernández Maldonado, Arturo J.; Rinaldi Ramos, Carlos; Curet Arana, María; Department of Chemical Engineering; De Jesús, Marco A.
    In the present work geometric optimizations, Metropolis Monte Carlo, and molecular dynamics simulations were done to study the feasibility of synthesizing Ni and Pt nanowires inside the pores of one dimensional zeolite frameworks. Conditions studied included different frameworks (cancrinite (CAN) and mordenite (MOR)), metal concentrations, silicon to aluminum ratios (Si/Al), and temperatures. It was found that the formation of metal nanowires is influenced by all these parameters. In general, larger sizes of interconnecting windows between main pore channels and side pockets (which is the case of MOR) could have a detrimental effect in the formation of nanowires inside zeolites. This effect can be reduced with the use of low Si/Al which can promote the displacement of guest metal atoms from the side pockets to the main pore channels, where metal nanowires could be formed. High metal concentrations also promote the migration of metal atoms to the pore channels, as well as the formation of elongated nanostructures. If these variables are managed adequately, an increase in temperature has a positive effect in the formation of metal nanowires because it increases the mobility of guest metal atoms.The viability of forming stable one dimensional Pt structures inside the pores of Virginia Polytechnic Institute Eight (VET) - type zeolites was also evaluated by using the above mentioned molecular simulations techniques, as well as grand canonical Monte Carlo. The resulting nanostructures were optimized and analyzed as formed both inside and outside of the zeolite template. The results show that theoretically it is possible to form relatively thermally stable ultrathin nanowires, when synthetized at a low Si/Al ratio and a high temperature. The results also show that the stable Pt nanowire structure obtained with the pcff forcefield was qualitatively similar to the one obtained with DFT.