Some Hanliufen Son Generation Mechanism In Interstellar Space Theory Research

The discovery of the interstellar molecule and its spectral line is honoured as one of the fourfamous inventions in the1960s. So far, scientists have found more than160interstellarmolecules, including H, C, N, P,S which are found widely in the earth.On the rigor condition ofextremely thin material and extremely low temperature, the study about the formation andtransformation process of these interstellar molecules which plays an important part in helpingdeduce the early formation process of the star and the origin of life. How to iminate theformation and consumption process of the molecules or ions is the goal of the study, in whichscientists are pursuing. Now this job has launched widely and thoroughly, developed aninterdiscipline subject-interstellar chemistry. Recently, the observation and discuss about theinterstellar molecules is improving observably. It attracts astronomical physical and chemicaland other fields that is finding and affirming new complex molecules and knowing theirformation and evolution process.In recent decades, the research of interstellar molecular structure and form has attracted theattention of chemical workers. The most reports are about the molecules containing of C, H, N,O elements, but few S element. So chemical scientists are interested in some sulfur interstellarmolecules and stability of the sulfur carbon cluster and so on. Up to now, sulfur interstellarmolecules have been observed one after another, but the research of their formation mechanismis very rare. So it is very significant to work up the molecular formation mechanism theoreticallythrough quantum chemical calculation.Therefore, the paper will study deeply the possible ways of forming some contain-sulfermolecules in interstellar space such as H₂CS、CS₂、CH₃SCHO, and some small molecules such asH₂O, HF, HCN, NH₃may have catalytic effect to the formation of them.Considering the above facets, we start our systemic study the formation mechanism ofcertain sulfur-containing molecules in interstellar space catalyzed by H₂O, HF, HCN, and NH₃.The thesis is consisted of three parts as follows:1. A DFT study for the mechanism of the formation of H₂CSDensity functional theory （DFT） has been used to study the mechanism of the reactionbetween CS and H₂, catalyzed by H₂O, NH₃, HCN and HF both in the gas phase and on a modelicy grain surface in the interstellar medium （ISM） at the B3LYP/6-311+G （d,p） levels.Comparison of the small molecular catalysis through the activation energy. Calculation result asfollowing：1.1Without Catalyst, the energy barrier of the reaction between CS and H₂is very high and it is usually difficult to occur. And the reaction is exothermic reaction. But the smallmolecular such as H₂O, HF，NH₃have the very good catalytic effect to the formation of H₂CSthrought hydrogen bonding interaction. The more the small molecule as the catalysts, the lowerthe potential barrier is in theory.1.2After calculation, the small molecular such as H₂O, HF，NH₃have the very goodcatalytic effect, but capability of Catalytic is different. The catalytic effect of HF almost equalNH₃, and they are better than water. Specific results as following:3HF>3H₂O>2HF>2H₂O>HF>NH₃>H₂O.2. A DFT study for the mechanism of the formation of methyl formate and methyl thiolformate2.1CO and CH₃OH which existed in the interstellar space as reactants, and smallmolecules such as H₂O, HF which also have been in the interstall space as catalysts, we havestudied the catalytic effect and the possibility of forming methyl formate in the interstall space.The results show that the catalytic effect of small molecules. The results showed that: while thereis a small molecule involved in the reaction, the activation energy decreases significantly, theorder of catalytic effectivenes of:3HF>2HF>3H₂O>2H₂O>HF>H₂O.2.2With CH₃SH, CO as reactants, and H₂O, HCN, NH₃, HF as catalysts, we find thetransition states and they are verfied by IRC. Based on the point of view of activation energy, wecompare the energy barrier and research these small molecules that could be the catalytic activity.The results showed that if there is a small molecule involved in the reaction, the activationenergy decreases significantly, the order of catalytic effectivenes of:3HF>2HF>3H₂O>2H₂O>HF>H₂O.3. A DFT study for the mechanism of the formation of Carbon disulfideCS and H₂S as reactants, some small molecules H₂O、2H₂O、HF、2HF as catalysts, the effecton the reaction have been studied by quantum mechnics calculation method. As the resultsindicate:3.1Without Catalyst, the energy barrier of the reaction between CS and H₂S is veryhigh and it is usually difficult to occur. The reaction is exothermic reaction. By calculation wefind the small molecules such as H₂O, HF，NH₃have very good catalytic effect to the formationof H₂CS throught hydrogen bonding interaction, but the catalytic effect is not obvious, so it isnot ideal. The more the small molecule as the catalysts, the lower the potential barrier is intheory.3.2By calaculating, the interstaller small molecules such as H₂O, HF which can formatehydrogen bond have a catalytic effect on the reaction. But different catalysts for catalyticcapacity is different. And catalysis of hydrogen fluoride is better than water molecules. The order of catalytic effectivenes of:2HF>2H₂O>HF>H₂O.