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Modelling of Chemical Processes
Al Mahmoud Alsheikh, Amer ; Bártlová,, Milada (oponent) ; Urban,, Ján (oponent) ; Žídek, Jan (vedoucí práce)
In this thesis the study of the fragmentation process of certain molecule is presented and it has been used to know the nature of fragmentation products. This work is concentrated to the calculation of fragmentation energy of the molecule using ab initio quantum chemistry methods and density functional theory (DFT) calculations and with a support by experiment. The influence of the computational method, basis set, and the geometry of molecule on simulation has been presented. It was compared the fragmentaion of methylphenylsilane (MPS), dimethylphenylsilane (DMPS) and trimethylphenylsilane (TMPS). The fragmentation was initiated by electron impact ionization (EII). The mass spectrometry technique was used to the analysis of the composition of fragmentation products from MPS and TMPS. The fragmentation products measured in this work were interpreted with respect to the ionization energy, appearance energies of fragments and bond dissociation energy of selected bonds. The results for MPS and TMPS were completed with DMPS previously published experimental data in order to have the series of similar compounds, which differ only by number of CH3 groups. Even the structurally similar molecules have significantly different fragmentation behavior. Comparison with the theoretical bond dissociation energies calculated using the DFT calculations has been presented. Using the combined experimental and theoretical approaches we have focused our recent studies to the common features as well as basic differences of the fragmentation schemes of all the three molecules. We proposed subtraction of two hydrogen atoms during plasma induced fragmentation process. The subtraction of H2 molecule, specific for MPS but rarely observed also in the other two compounds was also of high interest in our studies. It can run in two mechanisms: i. subtraction of two hydrogens one-by-one and ii. dissociation of H2 in one step. We can predict which mechanism is more probable according to the DFT calculated energy profile of reaction. The calculated predictions were in correlation with the composition of fragmentation products from experimental mass spectra.
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Modelling of Chemical Processes
Al Mahmoud Alsheikh, Amer ; Bártlová,, Milada (oponent) ; Urban,, Ján (oponent) ; Žídek, Jan (vedoucí práce)
In this thesis the study of the fragmentation process of certain molecule is presented and it has been used to know the nature of fragmentation products. This work is concentrated to the calculation of fragmentation energy of the molecule using ab initio quantum chemistry methods and density functional theory (DFT) calculations and with a support by experiment. The influence of the computational method, basis set, and the geometry of molecule on simulation has been presented. It was compared the fragmentaion of methylphenylsilane (MPS), dimethylphenylsilane (DMPS) and trimethylphenylsilane (TMPS). The fragmentation was initiated by electron impact ionization (EII). The mass spectrometry technique was used to the analysis of the composition of fragmentation products from MPS and TMPS. The fragmentation products measured in this work were interpreted with respect to the ionization energy, appearance energies of fragments and bond dissociation energy of selected bonds. The results for MPS and TMPS were completed with DMPS previously published experimental data in order to have the series of similar compounds, which differ only by number of CH3 groups. Even the structurally similar molecules have significantly different fragmentation behavior. Comparison with the theoretical bond dissociation energies calculated using the DFT calculations has been presented. Using the combined experimental and theoretical approaches we have focused our recent studies to the common features as well as basic differences of the fragmentation schemes of all the three molecules. We proposed subtraction of two hydrogen atoms during plasma induced fragmentation process. The subtraction of H2 molecule, specific for MPS but rarely observed also in the other two compounds was also of high interest in our studies. It can run in two mechanisms: i. subtraction of two hydrogens one-by-one and ii. dissociation of H2 in one step. We can predict which mechanism is more probable according to the DFT calculated energy profile of reaction. The calculated predictions were in correlation with the composition of fragmentation products from experimental mass spectra.
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