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First-principles study of stability of solid crystals
Pleskot, Ondřej ; Šesták, Petr (referee) ; Černý, Miroslav (advisor)
This work deals with a modeling of an electronic structure of solid crystals. Specifically, densities of valence electrons, and the density of states are calculated using first-principles code VASP for three crystals representing three different types of bonding. These are the metal bonding in a crystal of aluminum, the covalent bonding in a diamond crystal, and an ionic bonding in the crystal of rock salt. From calculated values of stress and crystal energy are then determined some macroscopic parameters of crystals, such as the equilibrium lattice parameter, the bulk modulus and the theoretical strength under isotropic tension.
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The effect of impurities on the interface cohesion in multilayers in transition metal nitrides
Češka, Jakub ; Zelený, Martin (referee) ; Černý, Miroslav (advisor)
This work deals with the study of transtition metal nitride multilayers using first-principles calculations. Objects of this study are three particular systems AlN / TiN, AlN / VN and TiN / VN. Studied systems are in the B1 structure with an interface along the (001) plane. The main goal is to unravel the effect of impurity on cohesion in these multilayers. The impurity in question is a substitutional O atom replacing N in the lattice. Preferred positions of these substitutions are predicted for three different concentrations of substitution impurity. These predictions are based on the energy balance of substitutions in different positions. Resulting preferred positions within the multilayer may differ depending on the oxygen concentration. In most cases, the preferred position is at the interface between the two nitrides. For such systems with oxygen impurity in the preferred position a cleavage energy along several (001) planes is calculated. The effect of the impurity on the value of cleavage energy depends on its concentration. In the case of AlN / TiN multilayer, a suitable concentration of the impurity may increase the cleavage energy of the weakest link in multilayer compared to clean multilayer. In other cases the presence of impurity either causes a decrease in the cleavage energy or does not significantly affect its value.
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Ab initio study of electronic structure of 2D materials
Pekár, Zdenko ; Nezval, David (referee) ; Černý, Miroslav (advisor)
This bachelor’s thesis begins with an overview of basic terminology and principles regarding transition metal dichalcogenides and density functional theory. The theoretical part then brings several examples of atomic configuration of such materials and aproximations for the exchange-correlation functional. The practical part focuses on computational simulation and optimization of cells for various phases of transition metal dichalcogenides and their combinations, and compares their properties to those found in scientific literature and also gathers new, so far untested information about these materials.
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The effect of impurities on the interface cohesion in multilayers in transition metal nitrides
Češka, Jakub ; Zelený, Martin (referee) ; Černý, Miroslav (advisor)
This work deals with the study of transtition metal nitride multilayers using first-principles calculations. Objects of this study are three particular systems AlN / TiN, AlN / VN and TiN / VN. Studied systems are in the B1 structure with an interface along the (001) plane. The main goal is to unravel the effect of impurity on cohesion in these multilayers. The impurity in question is a substitutional O atom replacing N in the lattice. Preferred positions of these substitutions are predicted for three different concentrations of substitution impurity. These predictions are based on the energy balance of substitutions in different positions. Resulting preferred positions within the multilayer may differ depending on the oxygen concentration. In most cases, the preferred position is at the interface between the two nitrides. For such systems with oxygen impurity in the preferred position a cleavage energy along several (001) planes is calculated. The effect of the impurity on the value of cleavage energy depends on its concentration. In the case of AlN / TiN multilayer, a suitable concentration of the impurity may increase the cleavage energy of the weakest link in multilayer compared to clean multilayer. In other cases the presence of impurity either causes a decrease in the cleavage energy or does not significantly affect its value.
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First-principles study of stability of solid crystals
Pleskot, Ondřej ; Šesták, Petr (referee) ; Černý, Miroslav (advisor)
This work deals with a modeling of an electronic structure of solid crystals. Specifically, densities of valence electrons, and the density of states are calculated using first-principles code VASP for three crystals representing three different types of bonding. These are the metal bonding in a crystal of aluminum, the covalent bonding in a diamond crystal, and an ionic bonding in the crystal of rock salt. From calculated values of stress and crystal energy are then determined some macroscopic parameters of crystals, such as the equilibrium lattice parameter, the bulk modulus and the theoretical strength under isotropic tension.
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