Currently, there are two main methodologies for the calculation of the electronic structure and properties of crystalline solids. Known as the Hartree-Fock Method (HF) and the Density Functional Theory (DFT) methods, they are based on two different theories for the numerical solution of the many electron Schrödinger equation. Unfortunately, in highly correlated electron systems like transition metal complexes, both the HF and DFT methods have severe shortcomings. In some cases they fail to provide the correct description of the electronic structure. <p>In general, the HF method overestimates the energy band gap due to the neglect of electron correlation effects and the incorrect description of electron interactions in the unoccupied orbitals. In contrast, even though electron correlation effects are implicitly included in the density functional, DFT often underestimates the band gap due to the improper treatment of the electron self-interaction. <p> To amend these problems, two approaches have been proposed. The deficiency in the HF scheme can be corrected using a hybrid method which adds exchange correlation energy borrowed from DFT to help reduce the band gap energy and bring the predictions in better agreement with experiment. To improve DFT, the LDA+U approach, which uses a model Hubbard-like Hamiltonian including an on-site repulsion parameter U, can be employed. This method is a convenient semi-quantitative way to efficiently calculate the band gap of insulators and semiconductors.<p> In this thesis, the electronic structure of YTiO₃ under pressure is investigated using the aforementioned approaches. The performance and reliability of these methods will be examined, compared and discussed.

Currently, there are two main methodologies for the calculation of the electronic structure and properties of crystalline solids. Known as the Hartree-Fock Method (HF) and the Density Functional Theory (DFT) methods, they are based on two different theories for the numerical solution of the many electron Schrödinger equation. Unfortunately, in highly correlated electron systems like transition metal complexes, both the HF and DFT methods have severe shortcomings. In some cases they fail to provide the correct description of the electronic structure. <p>In general, the HF method overestimates the energy band gap due to the neglect of electron correlation effects and the incorrect description of electron interactions in the unoccupied orbitals. In contrast, even though electron correlation effects are implicitly included in the density functional, DFT often underestimates the band gap due to the improper treatment of the electron self-interaction. <p> To amend these problems, two approaches have been proposed. The deficiency in the HF scheme can be corrected using a hybrid method which adds exchange correlation energy borrowed from DFT to help reduce the band gap energy and bring the predictions in better agreement with experiment. To improve DFT, the LDA+U approach, which uses a model Hubbard-like Hamiltonian including an on-site repulsion parameter U, can be employed. This method is a convenient semi-quantitative way to efficiently calculate the band gap of insulators and semiconductors.<p> In this thesis, the electronic structure of YTiO₃ under pressure is investigated using the aforementioned approaches. The performance and reliability of these methods will be examined, compared and discussed.

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The chemistry of actinides in aqueous solution is important, and it is essential to build adequate conceptual models and develop methods applicable for actinide systems. The complex electronic structure makes benchmarking necessary. In the thesis a prototype reaction of the water exchange reaction for uranyl(VI), for both ground and luminescent states, described with a six-water model, was used to study the applicability of density functional methods on actinides and different solvation models. An excellent agreement between the wave function methods CCSD(T) and MP2 was obtained in the ground state, implying that near-minimal CASPT2 can be used with confidence for the reaction in the luminescent state of uranyl(VI), while density functionals are not suited to describe energetics for this type of reaction. There was an ambiguity concerning the position of the waters in the second hydration sphere. This issue was resolved by investigating a larger model, and prop- erly used the six-water model was found to adequately describe the water exchange reaction. The effect of solvation was investigated by comparing the results from conductor-like polarizable continuum models using two cavity models. Scattered numbers made it difficult to determine which solvation model to use. The final conclusion was that the water exchange reaction in the luminescent state of uranyl(VI) should be addressed with near-minimal CASPT2 and a solvation model without explicit cavities for hydrogens. Finally it was shown that no new chemistry appears in the luminescent state for this reaction. The thesis includes a methodological investigation of a multi-reference density functional method based on a range separation of the two-electron interaction. The method depends on a universal parameter, which has been determined for lighter elements. It is shown here that the same parameter could be used for actinides, a prerequisite for further development of the method. The results are in that sense promising.

The dissertation thesis analyzes the debt burden on the prosperity of enterprise that operate in the territory of the Czech Republic, where the prosperity of the companies is expressed in equity capital profitability. The main aim is the empirical validation of the conclusions of financial leverage applied to the specific economic conditions of enterprises in the Czech Republic. The dissertation thesis is focused on the issue of the financial leverage on enterprises. First, the relation of return on equity and debt was evaluated Followed by an analysis of the relation of the debt ratio and a dynamic degree of financial leverage. Also a static degree of financial leverage with increasing debt was quantified. The operational objective was to assess a methodological diversity of quantification of static and dynamic model degrees of financial leverages. The validity of conclusions on the degree of financial leverage was assessed on the basic of the model simulating the impact of debt financing on earnings per share while changing the output (i.e., earnings before interest and taxes). The variance analysis of the return on equity indicator was performed using functional methods. The result was to quantify the effects of partial analytical indicators to the return on equity, the top-level indicator analyzed, mostly the influence of the dynamic degree of financial leverage indicators as a casual factor.

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No / Forumla chem. . A variety of 5-chloro-2(H)-1,4-oxazin-2-ones bearing a range of substituents at their 3- and 6-positions undergo Diels-Alder cycloaddition as a 2-azadiene component with electron-rich, electron-deficient, and electron-neutral dienophiles. These reactions proceed with moderate regio- and stereoselectivity to afford relatively stable and readily isolable bridged bicyclic lactone cycloadducts. Chemical manipulation of these cycloadducts affords highly substituted and functionally rich piperidines. The regio- and stereochemical preferences of the cycloadditions of 5-chloro-2(H)-1,4-oxazin-2-ones are investigated computationally using density functional theory (B3LYP/6-31G*).

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