Alkoxy Silane And A Silicon Oxide Reduction System The Quantum Chemical Calculations

With development of the modern industrial technology, energy consumptions are increasing, and environmental pollution has gone from bad to worse, the problems of renewable sources of energy have already drawn close attention from the countries all over the world. In the background of ultra pure silicon industry, the density functional theory (DFT) B3LYP are used in the structure and property studying of the industrial raw matical of solar grade silicon in this paper. Such as Si(OC2H5)4, Si(OCH3)4, HSi(OC2H5)3 and HSi(OCH3)3. We also made some fundamental researches of the thermodynamics and kinetics of the systems, which are composed of different reductants, alkoxy silanes and silicon monoxide. Finally, some important conclusions were gained by theory analysis. Such as structures and energies of all the stationary points on the potential energy surfaces, possible reaction channels, reaction mechanisms and major products. Some conclusions that were made in this thesis may be help for further theoretical and experimental studies of this kind of reactions. This paper consists of five chapters. The main results are summarized as follows:1. The structures, molecular property and chemical activity of the four alkoxy silanes were calculated by using B3LYP method with 6-311++G** basis set. It was found that the stability order of the four alkoxy silanes is Si(OC2H5)4>Si(OCH3)4>HSi(OC2H5)3>HSi(OCH3)3. By the study of their frontier orbital and NBO analysis, it was also show that the most active position of the for alkoxy silanes are Si-O and Si-H, especially in HSi(OC2H5)3 and HSi(OCH3)3.2. The B3LYP/6-311++G** method was used in the kinetic and thermodynamic study of the systems under the normal temperature and pressure conditions (298.15K, 1.0atm), which are composed of different reductants, alkoxy silanes and silicon monoxide. The AH, AE, AG of 32 systems were obtained. According to the second law of thermodynamics and the inindustrial condition, finally, some chemical reactions are screen out for the naxt study. Such as: 3C+Si(OCH3)4+2H2→Si+CO2+2CH3OH+2C2H4,3KH+HSi(OCH3)3→SiH4+3CH3OK and C+SiO→CO+Si.3. Under the normal temperature and pressure conditions (298.15K, 1.0atm), the B3LYP/6-311++G** method was used in the thermodynamic study of the chemical reaction:C+SiO→CO+Si. The geometries for all the stationary points on the potential energy surfaces were optimized fully. The transition state and reaction mechanism were verified by the IRC calculation and frequency analysis. It also showed that 46.7339kJ·mol-1 was needed for acrossing the energy barrier.