N~++H_2→NH~++H反应机理的热力学研究

应用量子化学耦合簇理论CCSD和MP2方法对文[1]提出的Titan大气中可能生成NH3的链式反应中第二个反应:N++H2→NH++H进行了热力学计算以及反应机理的分析研究.发现:(a)反应在Titan环境中不具有反应自发性,其转变温度为1797.6K,高于这个温度反应才有可能自发正向进行;(b)此反应的过渡态为线形,正反应活化能为118.833kJ.mol-1,在不同温度下,尤其是低温下反应的平衡常数很小;(c)由于此反应存在高的反应势垒,可以认为这6个链式反应不是在Titan大气的低温环境中自然合成N     

在Titan(土卫六)大气中生成环氧乙烷几个可能反应的量子力学计算研究

运用密度泛函方法和Gaussian-3理论，对Coll等人提出的Titan大气中可能生成环氧乙烷的5个反应进行了热化学计算和分析．结果表明：1．所有反应的反应焓变和吉布斯自由能变都小于零，反应都是放热反应，具有较大的自发反应趋势；2．在低温下反应的平衡常数很大，其数据显示反应在低温下正向进行的自发反应趋势更大．可以认为，在Titan大气的低温环境中自然合成环氧乙烷是很有可能的；3．由密度泛函方法和Gaussian-3理论两种方法的计算结果相吻合，互相印证了结论的可靠性．     

五个生成环氧乙烷的反应的热力学预测(英文)

运用密度泛函方法B3LYP/6-311+G(2df,2p)//B3LYP/6-31G(d)对文献[1]提出的Titan大气中可能生成环氧乙烷的五个反应在不同的温度和压强条件下进行了热力学计算和分析,发现:a)所有反应的反应焓变和吉布斯自由能变都小于零,反应都是放热反应,具有较大的自发反应趋势;在低温下反应的平衡常数很大,数据显示反应在低温下正向进行的自发反应趋势更大。b)对比生成环氧乙烷的同素异构体:乙醛和乙烯醇的计算结果,可以预测到在Titan大气的低温环境中自然合成环氧乙烷是很有可能的.     

SiH3+O2(3∑g)反应路径的理论研究

采用密度泛函B3LYP／6—311G^＊＊和高级电子相关耦合簇CCSD（T）／6-311G^＊＊。方法计算并研究了SiH3与O2（^3∑g）反应的机理，全参数优化了反应势能面上各驻点的几何构型，并用频率分析方法和内禀反应坐标（IRC）进行了计算，对过渡态进行了验证．结果表明：SiH3＋O2（^3∑g）反应可经多条路径和多个步骤，经缔合、氢转移和离解得到SiH3O2，SiH2O2＋H，SiH2O＋OH，SiH3O＋O，SiHO2＋H2等产物．     

关于硝胺分子中的N-NO2键强度的研究

用B3LYP,B3PW91,B3P86,CCSD配合不同大小的基组及CBS-Q方法计算了在分子NH2NO2,CH3NNO2,(CH3)2NNO2和RDX中离解掉二氧化氮的键离解能.通过对键离解能计算结果和实验结果的比较,作者发现由B3LYP,B3P86和CBS-Q不能计算出满意的键离解能,但是,CCSD和B3PW91方法能计算出与实验值吻合较好的键离解能.考虑到由B3PW91计算耗时要比CCSD方法少得多,因此,作者认为由B3PW91,并配合6-31G(d)基组作为计算这些硝胺分子键离解能的方法.     

LiX-（X=H，F，Cl）分子离子基态（X^2∑＋）势能函数与力常量

利用Gaussian09程序包中单双取代的耦合簇理论（CCSD）对LiX-（X=H，F，Cl）分子离子基态进行了几何优化和频率计算，进一步进行了单点能扫描计算．用最小二乘法拟合得到了LiX-（X=H，F，Cl）分子离子基态的Murrell—Sorbie势能函数，计算得到了LiX-（X=H，F，Cl）分子离子基态的力常量．     

气相中Mo~＋与CS_2反应的理论研究

用密度泛函理论中B3LYP方法详细研究了Mo＋（6S,4d5,4G,4d5）与CS2的反应机理.为了得到更为准确的活化能和反应的能量,在B3LYP优化好的结构的基础上,用耦合族理论（CCSD（T））计算了各个驻点的单点能.计算结果显示,活化C-S键的反应机理为是插入-消出机理.反应Mo＋（6S）＋CS2（1Σ）→MoS＋（4Σ-）＋CS（1Σ）在反应过程中经过六重态-四重态势能面交叉,我们确定势能面交叉点（CP）.所有的计算结果都和已有的理论和实验值进行了比较.     

气相中Ir^＋与CH4分子自旋禁阻反应中C—H键活化机理的理论研究

采用密度泛函理论和高级电子相关耦合簇方法,在CCSD（T）/6-311＋＋G（3df,3pd）//B3LYP/6-311＋G（d,p）的理论水平下,研究了3个自旋态势能面上自旋禁阻反应Ir^＋（^5F）＋CH4（^1A1）→IrCH2^＋（3A″）＋H2（1Σg^＋）的微观机理,通过自旋-轨道耦合的计算,讨论了势能面交叉和可能的自旋翻转过程.结果表明,Ir^＋与CH4的反应中不同势能面之间的“系间窜越”（ISC）将会发生,分子体系通过3次自旋翻转沿着热力学最有利的反应路径进行,最优的反应路径总放热量为44.64 kJ/mol.运用Harvey等的方法优化出最低能量交叉点（MECP）,并计算了MECP处相应的自旋-轨道耦合常数（SOC）,分别为346.95,2 545.62,2 990.98 cm^-1,较大的SOC值说明了自旋翻转是有效的.     

理论研究气相中NH+4(H2O)n(n=1～6)簇合物的结构特征

利用密度泛函理论中B3LYP方法．6—31G（d，p）基组对NH4^＋（H2O）n（n=1～6）簇合物进行几何优化。得到了稳定结构,本论文分拆了NH4^＋（H2O）n（n=1～6）簇合物的稳定结构．发现NH4^＋与H2O以线性氢键结合成的簇合物结构最稳定。其次是二叉结构，再次是三叉结构．     

CF_3C(O)F解离和异构化反应的热力学和动力学理论研究

用统计热力学方法和过渡态理论计算了ＣＦ３Ｃ（Ｏ）Ｆ解离反应的热力学和动力学函数及其随温度的变化．结果表明，低温下ＣＦ３Ｃ（Ｏ）Ｆ不会由解离反应而消耗；高温下自发并有一定的解离速率．另外，计算了重要反应物种的定容摩尔热容并做了多元线性拟合．     

Analysis of Pyrolysates for Polysulphoneamide Fiber by Py-GC/MS

Pyrolysis of polysulphoneamide fiber has been investigated using pyrolysis gas chromatography-mass spectroscopy at the different temperatures from 420℃ to 750℃. Its compositions of pyrolysates have been analyzed. At 420℃,pyrolysis of molecular chain could not completdy take place, 12 compounds of pyrolysis have only been identified. When the temperature increases, the compositions of pyrolysate increase sharply. Several compounds, especially sulfur dioxide, benzene, aniline, benzoic acid, 1,4-benzene dicaronitrile, N-phenyl-acetamide, diphenylamine, benzc[g] isoquinoline, N-phenyl-benzamide, hi-（ 4-cyanophenyl ）benzamide, could be formed. The degradation mechanisms which are determined by structure and amount of the thermal decomposition products are described. During pyrolysis, for polysulphoneamide, polymeric chain scissions take place as a successive removal of the monomer units from the polymeric chain. The chain scissions are followed by secondary reactions, which lead to a variety of compounds. Additional reactions can also take place during pyrolysis.     

Pyrolysis of Polytrimethylene Terephthalate （PTT） Fiber by Pyrolysis Gas Chromatography-Mass Spectroscopy

Pyrolysis of polytrimethylene terephthalate (PTT) fiber has been investigated by pyrolysis gas chromatography-mass spectroscopy in the temperature range from 400℃ to 750℃ in order to observe the possible effect of the temperature on its composition of pyrolysates. At 400℃, pyrolysis of molecular chain could occur, only 13 pyrolysates could be identified. The trimethylene moieties bound to the macromolecular core by ester bonds are cleaved at around 400℃. At 550℃ -750℃, pyrolysis of molecular chain could completely take place, 46 pyrolysates could be found. As the temperature increases, the compositions of pyrolysate are distinctly increased. Several compounds, especially benzoic acid, monopropenyl-p-phthalate, 2 - propenyl benzoate, di - 2 - propenyl ester, 1,4 -benzenedicarboxylic acid, benzene, 1, 5 - hexadiene, biphenyl and 1, 3 - propanediol dibenzoate could be formed. The thermal degradation mechanism, which is determined by structure and amount of the thermal decomposition products, are described. During pyrolysis of polytrimethylene terephthalate, polymeric chain scissions take place a peeling reaction as a successive removal of the dimer units from the polymeric chain. The chain scissions are followed by the elimination reaction, linkage action and secondary reactions, which bring about a variety fragment.     

High-temperature shock formation of N2 and organics on primordial Titan

Titan's atmosphere is composed primarily of N2 with a little methane and other organic molecules. But theoretical models suggest that the initial form of nitrogen in Titan's atmosphere may have been NH3. We have investigated the possible importance of strong shocks produced during high-velocity impacts accompanying the late states of accretion as a method for converting NH3 to N2. To simulate the effects of an impact in Titan's atmosphere we have used the focused beam of a high-power laser, a method that has been shown to simulate shock phenomena. For mixtures of 10%, 50% and 90% NH3 (balance CH4) we obtained yields of 0.25, 1, and 6 x 10(17) molecules of N2 per joule, respectively. We also find that the yield of HCN is comparable to that for N2. In addition, several other hydrocarbons are produced, many with yields in excess of theoretical high-temperature-equilibrium models. The above yields, when combined with models of the satellite's accretion, result in a total N2 production comparable to that present in Titan's atmosphere and putative ocean.     

气相中Mo+与CS2反应的理论研究

用密度泛函理论中B3LYP方法详细研究了Mo+(6S,4d5,4G,4d5)与CS2的反应机理.为了得到更为准确的活化能和反应的能量,在B3LYP优化好的结构的基础上,用耦合族理论(CCSD(T))计算了各个驻点的单点能.计算结果显示,活化C-S键的反应机理为是插入-消出机理.反应Mo+(6S)+CS2(1Σ)→MoS+(4Σ-)+CS(1Σ)在反应过程中经过六重态-四重态势能面交叉,我们确定势能面交叉点(CP).所有的计算结果都和已有的理论和实验值进行了比较.     

Analysis of Pyrolysates for Phenol Formaldehyde Resin by Py-GC/MS

Pyrolysis of phenol formaldehyde resin has been investigated by Pyrolysis Gas Chromatography-Mass Spectroscopy at the different temperatures from 500℃ to 750℃. Its composition of pyrclysates has been analyzed. Several compounds, especially benzene, toluene, p-xylene could only be formed above 500-550℃. Howerver, peak intensities for some pbend derivatives were decreased at the higher temperature. During pyrolysis, for thermo-setting phenol formaldehyde resins, polymeric chain scissions take place as a successive removal of the monomer units from the polymeric chain. The chain scissions are followed by secondary reactions, which leads to a variety of compounds. Addition reactions can also take place among the double-bond compounds during pyrolysis.     

F2,Cl2和Br2离解能的不同理论水平的比较计算

用DET—B3lyp、MP2、CCSD和CCSD(T)方法，分别在Lanl2dz、6—311G(d)、6—311(2d)和6—311(2df)基组下优化计算了F2、Cl2和Br2的离解能。对基组较小、精度较低的方法作大基组下的单点能校正计算。通过与实验值比较揭示了计算准确度与计算方法和基组的关系。     

The sequestration of ethane on Titan in smog particles

Saturn's largest satellite, Titan, has a dense atmosphere of nitrogen with a few per cent of methane. At visible wavelengths its surface is hidden by dense orange-brown smog, which is produced in the stratosphere by photochemical reactions following the dissociation of methane by solar ultraviolet light. The most abundant of the products of these reactions is ethane, and enough of it should have been generated over the life of the Solar System to form a satellite-wide ocean one kilometre deep. Radar observations have found specular reflections in 75 per cent of the surface spots observed, but optical searches for a sun-glint off an ocean have been negative. Here I explain the mysterious absence or rarity of liquid ethane: it condenses onto the smog particles, instead of into liquid drops, at the cold temperatures in Titan's atmosphere. This dusty combination of smog and ethane, forming deposits several kilometres thick on the surface, including the observed dunes and dark areas, could be named 'smust'. This satellite-wide deposit replaces the ocean long thought to be an important feature of Titan.     

A wind origin for Titan's haze structure

Titan, the largest moon of Saturn, is the only satellite in the Solar System with a dense atmosphere. Titan's atmosphere is mainly nitrogen with a surface pressure of 1.5 atmospheres and a temperature of 95 K (ref. 1). A seasonally varying haze, which appears to be the main source of heating and cooling that drives atmospheric circulation, shrouds the moon. The haze has numerous features that have remained unexplained. There are several layers, including a 'polar hood', and a pronounced hemispheric asymmetry. The upper atmosphere rotates much faster than the surface of the moon, and there is a significant latitudinal temperature asymmetry at the equinoxes. Here we describe a numerical simulation of Titan's atmosphere, which appears to explain the observed features of the haze. The critical new factor in our model is the coupling of haze formation with atmospheric dynamics, which includes a component of strong positive feedback between the haze and the winds.     

CH3CH2自由基与HNCO反应机理的理论研究

采用密度泛函理论的B3LYP方法,在6-311＋＋G（d,p）基组水平上研究了CH3CH2自由基与HNCO的微观反应机理,优化了反应过程中的反应物、中间体、过渡态和产物,为了获得更精确的能量信息,在QC ISD（T）/6-311＋＋G（d,p）水平上计算体系在反应通道各驻点的能量.振动分析结果和IRC分析结果证实了中间体和过渡态的真实性,计算所得的成键临界点电荷密度变化也确认了反应过程.对于CH3CH2自由基与HNCO反应,找到了10条反应通道.对结果的分析表明,其中生成烷基酰亚胺稳定分子的反应通道的控制步骤活化能最低,因此为主要通道,在该反应体系中氢迁移反应已不是主要的反应过程,但其活化能不高,也是能发生的.