Ab initio Calculation and Kinetic Study for the Abstraction Reaction of H with Sihcl3

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Theoretical Studies of the Reaction Mechanisms of CH3S＋NO2

The potential energy surface for the CH3S NO2 reaction has been studied using the ab initio G3(MP2) method. A variety of possible complexes and saddle points along the minimum energy reaction paths have been characterized at UMP2 (full)/6-31G(d) level. The calculations reveal dominating reaction mechanisms of the title reaction: CH3S NO2 firstly produce intermediate CH3SONO,then break up into CH3SO NO. The results are valuable to understand the atmospheric sulfur compounds oxidation mechanism.     

Theoretical Study on the Dehydrogenation Reaction of H2S by VS^＋ （^3Σ^-）

1 INTRODUCTION Interest in transition-metal sulfides arises from their significance in industrial catalysis and biolo- gy[1]. Transition-metal sulfides as versatile catalysts are often less susceptible to poisoning and show higher selectivity than their corresponding oxides[2]. In fact, the transition-metalion chemistry has been an active area for both experimental and theoretical studies[3～10]. Recently, Schwarz’s and Armentrout’s working groups[11, 12] have reported the experimenta…     

Theoretical Studies on the Si（001）-SiO2 Interface Structure

1 INTRODUCTION Silicon and its alloy have been widely applied in such fields as electronic industry, high-temperature structural ceramics, etc. In addition, the researches on silicon and its relevant materials greatly promote the rapid development of modern optics and infor- mation technology. Therefore, more and more at- tention is focused on the structure of silicon, oxide of silicon and the interfaces between silicon and metal or nonmetal. As an ideal passive film on the Si surface, S…     

New ab initio Potential Energy Surfaces for Cl（^2P3/2,^2P1/2）＋H2 Reaction

New global three dimensional potential energy surfaces for the Cl＋H2 reactive system have been constructed using accurate multireference configuration interaction calculations with a large basis set. The three lowest adiabatic potential energy surfaces correlating asymptotically with Cl（^2p）＋H2 have been transformed to adiabatic representation, which leads to a fourth coupling potential for non-linear geometries. In addition, the spin-orbit coupling surfaces have also been computed using the Breit-Pauli Hamiltonian. Properties of the new potential are described. Reaction dynamics based on the new potential agrees with the recent experimental results quite well.     

Theoretical Studies on Reaction Mechanisms of HNCS with NH （ X^3∑）

The reaction mechanisms of HNCS with NH（X^3∑ ） were theoretically investigated. The minimum energy paths （MEP） of the reaction were calculated by using the density functional theory（DFT） at the B3LYP/6-311 ＋ ＋ G^＊＊ level. The equilibrium structural parameters, the harmonic vibrational frequencies, the total energies, and the zeropoint energies（ZPE） of all the species were calculated. The single-point energies along the MEP were further refined at the QCISD（T）/6-311 ＋ ＋ G^＊ ＊ level. It was found that the mechanisms of the HNCS ＋ NH（X^3∑） reaction involve two channels producing the HNC ＋ HNS and the N2H2 ＋ CS products. Channel 1 plays a dominant role and the HNC ＋ HNS are the main preduets. The reaction is exothermie.     

Kinetic Studies on the Reaction of Sodium Hexacyanoferrate（ll） Complex with Peroxydisulfate Anion

The oxidation of Na₄Fe(CN)₆ complex by S₂O anion was found to follow an outer‐sphere electron transfer mechanism. We firstly carried out the reaction at pH=1. The specific rate constants of the reaction, k_ox, are (8.1±0.07)×10^?2 and (4.3±0.1)×10^?2 mol^?1·L·s^?1 at μ=1.0 mol·L^?1 NaClO₄, T=298 K for pH=1 (0.1 mol·L^?1 HCl0₄) and 8, respectively. The activation parameters, obtained by measuring the rate constants of oxidation 283–303 K, were ΔH^≠=(69.0±5.6) kJ·mol^?1, ΔS^≠=(?0.34±0.041)×10² J·mol^?1·K^?1 at pH=l and ΔH^≠=(41.3±5.5) kJ·mol^?1, ΔS^≠=(?1.27±0.33)×10² J·mol^?1·K^?1 at pH=8, respectively. The cyclic voltammetry of Fe(CN) shows that the oxidation is a one‐electron reversible redox process with E_1/2 values of 0.55 and 0.46 V vs. normal hydrogen electrode at μ=1.0 mol·L^?1 LiClO₄, for pH=1 and pH=8 (Tris). respectively. The kinetic results were discussed on the basis of Marcus theory.     

Theoretical Investigation for the Abstraction Reaction of H with (CH_3)_3GeH

The reaction of H atom with (CH3)3GeH is considered to play important role in chemical vapor deposition (CVD) processes used in the semiconductor industry 1-2. The reaction mechanism and kinetics nature for this reaction are therefore essential input data for computer-modelling studies directed towards obtaining an understanding of the factors controlling CVD processes. However, despite its importance, the kinetics work about this reaction was very limited. Only two groups studied exper…     

H原子和(CH_3)_2SiH_2抽提反应的理论研究

采用UMP2 / 6- 3 1G(d)理论水平优化了H原子和 (CH3) 2 SiH2 抽提反应势能面上的所有驻点 ,并在此水平基础上进行了内禀反应坐标 (IRC)的计算 ,得到该反应的反应途径 (MEP) .应用变分过渡态理论及最小能量途径半经典绝热基态隧道效应校正 (MEPSAG)、小曲率半经典绝热基态隧道效应校正 (SCSAG)等方法对上述反应进行了动力学研究 ,期望从理论上提供一套温度范围较宽、精度较高的动力学数据 ,为阐明反应机理和解释实验结果提供理论依据     

SiH3+O(3P)反应机理的理论研究

The reaction for SiH3+O(3P) was studied by ab initio method. The geometries of the reactants, intermediates, transition states and products were optimized at MP2/6-311+G(d,p) level. The single point calculations for all the stationary points were carried out at the QCISD(T) /6-311+G(d,p) level using the MP2/6-311+G(d,p) optimized geometries. The results of the theoretical study indicate that the major pathway is the SiH3+O(3P)→IM1→TS3→IM2→TS8→HOSi+H2. The other minor products include the HSiOH+H, H2SiO+H and HSiO+H2. Furthermore, the products HOSi, HSiO and HSiOH(cis) can undergo dissociation into the product SiO. In addition, the calculations provide a possible interpretation for disagreement about the mechanism of the reaction SiH4+O(3P). It suggests that the products HSiOH, H2SiO and SiO observed by Withnall and Andrews are produced from the secondary reaction SiH3+O(3P) and not from the reaction SiH4+O(3P).     

Kinetic calculation for the reaction of H with Si_2H_6 using the variational transition state theory

The reaction of disilane with atomic hydrogen has been studied. This reaction involves both substitution and abstraction. Calculations show that the hydrogen abstraction is the strongest competing channel. The canonical variational transition state theory with a small curvature tunneling correction (SCT) has been used for the kinetic calculation. The theoretical results are in good agreement with the available experimental data. Comparing the reactions of atomic hydrogen with disilane and silane, it can be seen that the reactivity of the Si-H bond is higher in Si2H6than that in SiH4.     

CH3CH2+O(3P)反应机理的理论研究

The reaction for CH3CH2+O(3P) was studied by ab initio method. The geometries of the reactants, intermediates, transition states and products were optimized at MP2/6-311+G(d,p) level. The corresponding vibration frequencies were calculated at the same level. The single-point calculations for all the stationary points were carried out at the QCISD(T)/6-311+G(d,p) level using the MP2/6-311+G(d,p) optimized geometries. The results of the theoretical study indicate that the major products are the CH2O＋CH3, CH3CHO+H and CH2CH2+OH in the reaction. For the products CH2O＋CH3 and CH3CHO+H, the major production channels are A1: (R)→IM1→TS3→(A) and B1: (R)→IM1→TS4→(B), respectively. The majority of the products CH2CH2+OH are formed via the direct abstraction channels C1 and C2: (R)→TS1(TS2)→(C). In addition, the results suggest that the barrier heights to form the CO reaction channels are very high, so the CO is not a major product in the reaction.     

C3H2环丙烯基自由基与O(3P)反应机理的理论研究

本文用量子化学密度泛函方法对C3H2 (环丙烯基自由基)与O(3P)反应的机理进行了理论研究。在B3LYP/6-311++G**计算水平上优化了各驻点（过渡态,中间体,产物）的几何结构,在QCISD(T)/6-311++G**水平下计算了各物质的单点能量,在两种水平下计算了298K和600K时的能量。计算结果表明：C3H2 + O(3P) 反应可以生成P1 (C2H +HCO),P2 (C2H2 + CO) 和P3 (HC3O+H)三种产物。生成P1反应通道的能垒最低,即P1为主要产物,与实验的结果一致。产物P1可以通过路径：R→ IM1→ IM2→ P1获得。本文详细地讨论了C3H2 + O(3P) 的反应机理,并从理论上对实验结果进行了验证。研究结果有助于深入理解C3H2 + O(3P)反应机理以及C3H2在大气中的燃烧过程。     

Theoretical study and rate constant calculation for the reactions of SH (SD) with Cl2, Br2, and BrCl

The mechanisms of the SH (SD) radicals with Cl2 (R1), Br2 (R2), and BrCl (R3) are investigated theoretically, and the rate constants are calculated using a dual-level direct dynamics method. The optimized geometries and frequencies of the stationary points are calculated at the MP2/6-311G(d,p) and MPW1K/6-311G(d,p) levels. Higher-level energies are obtained at the approximate QCISD(T)/6-311++G(3df, 2pd) level using the MP2 geometries as well as by the multicoefficient correlation method based on QCISD (MC-QCISD) using the MPW1K geometries. Complexes with energies less than those of the reactants or products are located at the entrance or the exit channels of these reactions, which indicate that the reactions may proceed via an indirect mechanism. The enthalpies of formation for the species XSH/XSD (X = Cl and Br) are evaluated using hydrogenation working reactions method. By canonical variational transition-state theory (CVT), the rate constants of SH and SD radicals with Cl2, Br2, and BrCl are calculated over a wide temperature range of 200-2000 K at the a-QCISD(T)/6-311++G(3df, 2pd)//MP2/6-311G(d, p) level. Good agreement between the calculated and experimental rate constants is obtained in the measured temperature range. Our calculations show that for SH (SD) + BrCl reaction bromine abstraction (R3a or R3a') leading to the formation of BrSH (BrSD) + Cl in a barrierless process dominants the reaction with the branching ratios for channels 3a and 3a' of 99% at 298 K, which is quite different from the experimental result of k3a'/k3' = 54 +/- 10%. Negative activation energies are found at the higher level for the SH + Br2 and SH + BrCl (Br-abstraction) reactions; as a result, the rate constants show a slightly negative temperature dependence, which is consistent with the determination in the literature. The kinetic isotope effects for the three reactions are "inverse". The values of kH/kD are 0.88, 0.91, and 0.69 at room temperature, respectively, and they increase as the temperature increases.     

Theoretical study on the insertion reactions of Ti+(2F) with HF,HCl, H2O,H2S,NH3, PH3, CH4, and SiH4

The insertion reactions of the titanium atom cation Ti⁺(²F) into HF, HCl, H₂O, H₂S, NH₃, PH₃, CH₄, and SiH₄ have been studied by ab initio molecular orbital theory. All these reactions involve the initial formation of an intermediate complex followed by a hydrogen migration process via a transition state to inserting product. The Ti⁺(²F) insertion into eight compounds' reactions show that the reaction with hydride of the right‐hand group is more exothermic than that of the left‐hand group and has a lower overall barrier, and that the reaction with the second‐row hydride has a lower overall barrier and is less exothermic than with the first‐row hydride. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 75: 47–54, 1999     

A dual-level ab initio and hybrid density functional theory dynamics study on the unimolecular decomposition reaction C2H5O-->CH2O + CH3

We present a direct ab initio and hybrid density functional theory dynamics study of the thermal rate constants of the unimolecular decomposition reaction of C2H5O-->CH2O + CH3 at a high-pressure limit. MPW1K/6-31+G(d,p), MP2/6-31+G(d,p), and MP2(full)/6-31G(d) methods were employed to optimize the geometries of all stationary points and to calculate the minimum energy path (MEP). The energies of all the stationary points were refined at a series of multicoefficient and multilevel methods. Among all methods, the QCISD(T)/aug-cc-pVTZ energies are in good agreement with the available experimental data. The rate constants were evaluated based on the energetics from the QCISD(T)/aug-cc-pVTZ//MPW1K/6-31+G(d,p) level of theory using both microcanonical variational transition state theory (microVT) and RRKM theory with the Eckart tunneling correction in the temperature range of 300-2500 K. The calculated rate constants at the QCISD(T)/aug-cc-pVTZ/MPW1K/6-31+G(d,p) level of theory are in good consistent with experimental data. The fitted three-parameter Arrhenius expression from the microVT/Eckart rate constants in the temperature range 200-2500 K is k = 2.52 x 10(12)T(0.41)e(-8894.0/T) s(-1). The falloff curves of pressure-dependent rate constants are performed using master-equation method within the temperature range of 391-471 K. The calculated results are in good agreement with the available experimental data.     

亚烷基卡宾及取代亚烷基卡宾与环氧乙烷反应的量子化学研究

用量子化学的密度泛函理论(DFT)在6-311G(d,p)水平上对亚烷基卡宾及取代亚烷基卡宾与环氧乙烷的氧转移反应机理进行了系统的研究. 用IRC对过渡态进行了确认. 并用组态混合模型讨论了反应势垒(ΔE^≠)与XYC＝C:的单-三态能量差ΔE_ST之间的关系, 结果表明, 取代基的电负性是控制反应的主要因素, 取代基的电负性越大, 取代基越多, π电子给予体越多, 单-三态能量差ΔE_ST就越小, 该反应的活化能就越小, 反应越容易发生. 同时还研究了该反应中环氧乙烷中C—O键的解离过程. 发现两个C—O键解离是一个不同步的协同过程.