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Theoretical Investigation of the Zeolite Hydrolysis under Realistic Conditions
Jin, Mengting ; Grajciar, Lukáš (advisor) ; Chizallet, Céline (referee) ; Piskorz, Witold (referee)
Zeolites are one of the most widely used and one of the most industrially important materials. They are utilized in a variety of commercial applications, particularly in heterogeneous catalysis, adsorption/separations applications and as ion exchangers. Zeolites are stable when exposed to water or water vapor at ambient conditions and exhibit high thermal stability. However, zeolites can be partially or even fully hydrolyzed under certain conditions. This hydrolytic instability of zeolites can be considered both a major problem in some applications and a useful means to tune catalyst properties in the others. However, the thorough studies of the hydrolytic mechanisms under realistic conditions (high water loading, alkaline conditions, high heteroatom concentrations, etc.) and employing realistic models (dynamical simulation of ab initio accuracy) is mostly lacking. This dissertation uses the ab initio calculations to systematically study the hydrolysis mechanism of zeolites under realistic conditions, including: (1) hydrolysis mechanism of germanosilicate zeolite UTL, (2) hydrolysis of siliceous zeolite CHA under alkaline conditions, and (3) identification of the nature of framework-associated Al(Oh) species in aluminosilicate zeolite CHA under wet conditions. The main results obtained are as...
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Novel prospective materials for nonlinear optics
Votrubcová, Iveta ; Němec, Ivan (advisor) ; Nižňanský, Daniel (referee)
This bachelor thesis is focused on the preparation of novel materials for nonlinear optics and includes studies of twenty-eight crystallization systems, which provide twelve crystalline compounds - salts of 2-aminopyrimidine and 2,4,6-triaminopyrimidine with inorganic oxo-acids (nitric, perchloric, sulfuric, phosphoric, phosphorous). Studied materials have been identified and defined by a vibrational spectroscopy and X-ray structure analysis. From the prepared materials only aminopyrimidinium (1+) hydrogen phospite fulfils the symmetry conditions for the second harmonic generation. Efficiency of the second harmonic generation was afterwards defined for the powdered sample relatively to the KDP and urea standards.
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Theoretical Investigation of Low-dimensional Magnetic Materials
Li, Shuo ; Grajciar, Lukáš (advisor) ; Frauenheim, Thomas (referee) ; Jelínek, Pavel (referee)
Low-dimensional (D) materials, such as graphene, transition metal dichalcogenides and chalcogenide nanowires, are attractive for spintronics and valleytronics due to their unique physical and chemical properties resulting from low dimensionality. Emerging concepts of spintronics devices will greatly benefit from using 1D and 2D materials, which opens up new ways to manipulate spin. A majority of 1D and 2D materials is non-magnetic, thus their applications in spintronics are limited. The exploration, design and synthesis of new 1D and 2D materials with intrinsic magnetism and high spin-polarization remains a challenge. In addition, the valley polarization and spin-valley coupling properties of 2D materials have attracted great attention for valleytronics, which not only manipulates the extra degree of freedom of electrons in the momentum space of crystals but also proposes a new way to store the information. The computational investigation of magnetic and electronic properties of low-dimensional materials is the subject of this thesis. We have systematically investigated geometric, electronic, magnetic and valleytronic properties of several 2D and 1D materials by using the density functional theory. These investigations not only theoretically show rich and adjustable magnetic properties of...
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Novel prospective materials for nonlinear optics
Votrubcová, Iveta ; Nižňanský, Daniel (referee) ; Němec, Ivan (advisor)
This bachelor thesis is focused on the preparation of novel materials for nonlinear optics and includes studies of twenty-eight crystallization systems, which provide twelve crystalline compounds - salts of 2-aminopyrimidine and 2,4,6-triaminopyrimidine with inorganic oxo-acids (nitric, perchloric, sulfuric, phosphoric, phosphorous). Studied materials have been identified and defined by a vibrational spectroscopy and X-ray structure analysis. From the prepared materials only aminopyrimidinium (1+) hydrogen phospite fulfils the symmetry conditions for the second harmonic generation. Efficiency of the second harmonic generation was afterwards defined for the powdered sample relatively to the KDP and urea standards.
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