Theoretical Study of the AlCl Disproportionation Reaction Mechanism on the Al(100) Surface

The surface disproportionation reaction mechanism of aluminum subchloride on the aluminum (100) surfaces has been investigated by the plane-wave density functional theory (DFT).Three kinds of possible reaction mechanism of AlCl disproportionation reaction on the aluminum (100) surfaces have been taken into account.The structures of reactants and products have been optimized,transition states have been confirmed and activation energies have been calculated.The adsorption energy of reactants and desorption energy of products have been determined.All of these have been employed to confirm the reaction mechanism and the rate determining step of AlCl disproportionation reaction on the aluminum (100) surfaces.     

Cu催化水煤气的变换反应机理

采用密度泛函理论(DFT), 对Cu催化水煤气变换反应三种可能的微观机理进行了理论研究. 在GGA-PW91理论水平下优化了反应通道上各驻点(反应物、中间体、过渡态和产物)的几何构型, 并通过频率分析对过渡态进行了验证. 研究结果表明, 甲酸根机理的可能性最小, 羧基机理与氧化还原机理的可能性较大, 且与氧化还原机理相比, 羧基机理因在反应过程中有中间体COOH(s)生成, 且它与OH(s)发生歧化反应仅需越过3.8 kJ·mol-1的活化能垒, 所以反应更易遵循这条路径进行.     

Ru(II)催化有机叠氮与炔反应机理的理论研究

采用密度泛函理论, 对在Ru(II)催化剂存在下, 有机叠氮化合物和末端炔的反应机理作了深入理论研究. 在B3LYP/LANL2DZ水平上, 对该反应体系中势能面各驻点的几何构型进行了全优化计算, 并经振动频率分析确定了过渡态和中间体, 通过内禀反应坐标(IRC)的计算, 确认了反应物、中间体、过渡态和产物的相关性. 对多个反应通道的协同反应以及分步反应进行了研究. 结果表明: 协同反应通道Ic和分步反应通道IIc是反应能垒较低的反应通道, 活化自由能较其它反应通道低, 有利于1,5-二取代1,2,3-三唑的生成, 具有特定的区域选择性, 与实验结果吻合.     

D-苯丙氨酸与Cu＋(1S0, 3d10)气相反应理论研究

用量子化学密度泛函(DFT)方法研究D-苯丙氨酸与一价基态金属阳离子Cu^＋在气相中反应的机理. 在B3LYP/6-31G*水平上, 优化了反应包含的4个反应通道的反应物、中间体、过渡态和产物的几何构型, 并采用B3LYP/DZVP, B3LYP/[6-311＋G**(C,H,O)＋Lanl2dz(Cu)], B3LYP/6-311＋G**, MP2/6-311＋G** 等方法对各驻点进行了单点能计算. 通过对计算结果的分析, 获得了其单重态反应势能面的一般轮廓、各驻点几何构型优化参数, 明确了其反应机理.     

Cl+CH3OCl反应机理的理论研究

采用从头算方法,对多通道反应体系Cl+CH3OCl的反应机理进行了理论研究.在MP2/6-31+G(d,p)水平下优化了反应物、络合物、产物和过渡态的几何构型,并对得到的平衡几何构型进行了简谐振动频率分析.在相同水平下以过渡态为出发点,通过内禀反应坐标(IRC)理论计算了反应的最小能量路径.并且在MC-QCISD(T)/6-31G(d)高水平下进行了单点能量校正.研究结果表明,该反应存在4条可行的反应通道,其中生成HCl和CH2OCl的通道为主反应通道,其他反应通道为次反应通道.     

多通道反应O(3P)＋CH2F的理论研究

用密度泛函理论研究了氧原子与氟代甲基自由基的反应.反应中出现的所有物种的平衡构型用B3LYP方法在6-311＋＋G（2d, 2p）基组水平上进行了优化，同时对各物种进行了频率分析；在同一理论水平上计算了各反应通道的势能面变化，分析了反应物、中间体、过渡态、产物的振动模式随反应途径的变化关系，阐明了该多通道反应的反应机理.     

Ab initio simulation of the grafting of phenylacetylene on hydrogenated surfaces of crystalline silicon catalyzed by a Lewis acid

Car-Parrinello simulations have been carried out to identify the grafting mechanism of phenylacetylene, a prototypical alkyne, on the hydrogenated surfaces of crystalline silicon, catalyzed by a Lewis acid (AlCl3). To this purpose, we have made use of a new technique, metadynamics, devised recently to deal with complex chemical reactions in first principles simulations. The reaction mechanism, leading to a styrenyl-terminated surface, turns out to be equivalent to the corresponding gas-phase hydrosilylation reaction by silanes that we have identified in a previous work. The activation energies for the surface reactions (0.43, 0.42, 0.35 eV, for H-Si(111), H-Si(100)2 x 1, and H-Si(100)1 x 1, respectively) are very close to that of the corresponding gas-phase reaction (0.37 eV). The estimated activation free energy at room temperature is sufficiently low for the grafting reaction to be viable at normal conditions and at low coverage on the crystalline silicon surfaces, as already well documented to occur on the surface of porous silicon. However, the conformation of the transition state shadows a large area of the surface, which might contribute to making the grafting process self-limiting.     

Theoretical study of the reaction of Sc with SCO in gas phase

In order to elucidate the mechanism of reaction M⁺ + SCO, both triplet and singlet potential energy surfaces (PESs) for the reaction of Sc⁺ + SCO have been theoretically investigated using the DFT (B3LYP/6-311+G*) level of theory. The geometries for reactants, intermediates, transition states and products were completely optimized. All the transition states were verified by the vibrational analysis and the intrinsic reaction coordinate calculations. The involving potential energy curve-crossing dramatically affects reaction mechanism, reaction rate has been discussed, and the crossing points (CPs) have been localized by the approach suggested by Yoshizawa et al. The present results show that the reaction mechanism are insertion–elimination mechanism both along the C–S and C–O bond activation branches, but the C–S bond activation is much more favorable in energy than the C–O bond activation. All theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction.     

Density Functional Study on the Mechanism of Collision Reaction among Protons, N2 and Water Vapor

The mechanism of collision reaction among protons, N2 and water vapor was theoretically studied using Density Functional Theory. The geometries of reactants, transition states, intermediates and products were optimized at the B3LYP/6-311 G^** level by the BERNY gradient analysis method. Transition states and intermediates have been identified by vibrational frequency analysis. The relationship among reactants, intermediates, transition states and products was affirmed by IRC calculation. The variations of energy and geometry along the IRC-determined reaction paths were described. The possible reaction pathways were represented and the optimal one was decided from the viewpoint of energy.     

硅炔氢加成生成甲硅烷基硅烯的量子化学研究

利用量子化学从头算和密度泛函理论(DFT), 研究了硅炔和氢气分子加成生成甲硅烷基硅烯的反应机理. 在B3LYP/6-311G**水平上, 全参数优化了反应通道上各驻点(反应物、过渡态和产物)的几何构型, 计算出了它们的振动频率和零点振动能(ZPVE), 并对它们进行了振动分析, 以确定过渡态的真实性. 各物质总能量由QCISD(T)/6-311G**// B3LYP/6-311G**给出, 并对能量进行了零点能校正. 计算表明, 硅炔与氢分子加成反应可生成稳定的甲硅烷基硅烯. 热力学与动力学计算表明, 反应过程是一个放热、熵减少而自发趋势和反应程度较大的反应.     

水解聚合铝溶液中Al5和Al9的制备及初步表征

以相图理论为指导,采用铝粉、水合氯化铝和水为原料,创造氯化铝不断水解的条件,通过调整反应温度、原料配比及溶液碱化度,经蒸发、结晶制成了铝盐水解聚合产物中的两种中间产物：水合氯化五聚铝AlCl3•4Al(OH)3•7.5H2O和水合氯化九聚铝2AlCl3•7Al(OH)3•18H2O,分别采用粉末XRD物相分析、化学分析和IR对其进行了表征.以化学分析为主要监测手段,对AlCl3•4Al(OH)3•7.5H2O和2AlCl3•7Al(OH)3•18H2O形态过程进行了研究,结果表明,温度对于产物的行成及性能有很大的影响,并且反应随温度的变化基本上是一个可逆的过程,同时,实验表明 75℃为AlCl3•4Al(OH)3•7.5H2O和2AlCl3•7Al(OH)3•18H2O析出的最佳温度,该温度下产物的产率较高且结晶状态良好.     

O~3＋NH→HNO＋O~2反应机理的量子化学研究

用密度泛函(DFT)的B3LYP方法(6－31++G^*^*)研究了臭氧与NH自由基反应的微观机理,优化得到反应途径上的反应物,过渡态,中间体和产物的构型,通过振动分析对过渡态和中间体进行了确认。对单点用QCISD(T)/6－31++G^*^*方法计算能量,同时进行零点能校正。研究结果表明：NH与O~3反应有两条不同的反应通道,且均表现为亲电反应特征,两条不同的反应均为强放热反应。     

HS和HONO反应机理的研究

采用密度泛函和耦合簇理论方法研究了HS与HONO的反应机理.在B3LYP/6-311+G(2df,2p)水平上对HS+HONO反应中的所有物种进行了几何构型优化和频率分析,通过内禀反应坐标(IRC)确认了反应物、过渡态、中间体和产物之间的相关性;采用CCSD(T)/6-311+G(2df,2p)方法获得了各物种的单点能.计算结果表明:HS+HONO的主要反应通道为HS+cis-HONO→p2-cis-IM1→p2-cis-TS→p2-IM2→P2(H_2S+NO_2),其反应活化能为71.26kJ·mol~(-1).     

激发态Ti＋(3d14s2)与丙炔醇气相反应理论研究

用量子化学密度泛函(DFT)方法研究了激发态Ti^＋(3d¹4s²)与丙炔醇(PPA)气相反应的机理. 在B3LYP/DZVP水平上, 优化了反应的两个通道的反应物、中间体、过渡态和产物的几何构型, 并在MP4/[6-311＋G**(C,H,O)＋Lanl2dz (Ti)]水平上计算了各驻点的单点能量. 为了确证过渡态的真实性, 在B3LYP/DZVP水平上进行了内禀坐标(IRC)计算和频率分析, 获得了二重态反应势能面, 确定了反应机理. 研究结果表明生成产物为[C₃H₃O]^＋和Ti—H的通道是主要反应途径.     

Molecular Beam Studies on the Laser-Enhanced Surface Reaction of GaAs(100) with Chlorine

A cw supersonic Cl₂ molecular beam coupled with an angle-resolved time-of-flight (TOF) technique has been used to investigate the laser-enhanced surface reaction of GaAs(100) with chlorine. The mass and velocity distributions of the major reaction products under 1064 nm laser irradiation have been measured as a function of laser fluence, detection angle, surface temperature and normal component of the translational energy of the incident chlorine molecules. It has been found that increasing both laser fluence and the translational energy of incident chlorine molecules markedly enhance mis surface reaction. The measured flux angular distributions of major reaction products can be fit satisfactorily with a bi-cosine function. Measurements of the mass and angular distributions of reaction products by a modulated molecular beam mass spectrometry show that the surface temperature effect is obvious for the Cl₂/GaAs(100) “dark” thermal reaction. A direct activated dissociative chemisorption is proposed for the mechanism of Cl₂ chemisorption on the GaAs(100) surface.     

Gas-phase Boudouard disproportionation reaction between highly vibrationally excited CO molecules

The gas-phase Boudouard disproportionation reaction between two highly vibrationally excited CO molecules in the ground electronic state has been studied in optically pumped CO. The gas temperature and the CO vibrational level populations in the reaction region, as well as the CO₂ concentration in the reaction products have been measured using FTIR emission and absorption spectroscopy. The results demonstrate that CO₂ formation in the optically pumped reactor is controlled by the high CO vibrational level populations, rather than by CO partial pressure or by flow temperature. The disproportionation reaction rate constant has been determined from the measured CO₂ and CO concentrations using the perfectly stirred reactor (PSR) approximation. The reaction activation energy, 11.6 ± 0.3 eV (close to the CO dissociation energy of 11.09 eV), was evaluated using the statistical transition state theory, by comparing the dependence of the measured CO₂ concentration and of the calculated reaction rate constant on helium partial pressure. The disproportionation reaction rate constant measured at the present conditions is k_f = (9 ± 4) × 10⁻¹⁸ cm³/s. The reaction rate constants obtained from the experimental measurements and from the transition state theory are in good agreement.     

Reaction mechanism of HSH and CH3SH with NH2CH2COCH2X (X = F and Cl) molecules

The reaction mechanism of model compounds H₂S and CH₃SH for cysteine proteases with NH₂CH₂COCH₂X (X = F and Cl) molecules has been investigated using DFT methods with B3LYP and B3PW91 hybrid density functionals at 6‐31+G* basis sets. The single point energy has been calculated for the above reactions with B3LYP and B3PW91 functionals using aug‐cc‐PVDZ infinite basis set in both gas and solution phases. The intrinsic reaction coordinates calculations have been performed to confirm that each transition state is linked by the desired reactants and products. The geometries and relative energies for various stationary points have been determined and discussed. The zero point vibrational energy corrections have been made to predict the reliable energy. The negative value of reaction energy indicates that the overall reaction profile is found to be exothermic. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

C-甲基硝酮与硝基乙烯1,3-偶极环加成反应及其溶剂效应的理论研究

用密度泛函B3LYP方法研究了硝基乙烯与C-甲基硝酮的1,3-偶极环加成反应, 并利用自洽反应场方法(SCRF)计算了环已烷与乙腈这两种溶剂分别对反应所产生的 影响。该反应进行时反应物的接近有四种方式,对气相情况下和上述两种溶剂中的 反应物、四种可能产物及其相应过渡态和反应前期复合物构型分别进行了优化并计 算了振动频率。四个反应均为放热反应,且均具有很低的反应势垒,四种产物均容 易生成。但在气相反应和以环已烷为溶剂的情况下,生成的产物中endo-4型产物略 占优势;而在乙腈溶剂中得到endo-5型略占优势的产物。