共查询到20条相似文献,搜索用时 343 毫秒
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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. 相似文献
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本文用RHF/STO-3G解析梯度方法研究了钠卤类硅烯H2SiNaX(X=F,Cl)势能面的主要特征, 得到了它们的几种平衡构型及其异构化的过渡态构型。与锂卤类硅烯相似, 三元环构型和P-配合物构型是最稳定的构型; 其它的两种构型-σ-配合物和经典"四面体", 也是势能面上的极值点, 但能量相对较高, 不稳定。文中对各构型的特点进行了分析。 相似文献
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Ziyan Zhou Xiumei Pan Xue Wu Zhongmin Su Yuhe Kan Yuzhong Xie 《International journal of quantum chemistry》2004,98(6):515-521
The isomerization reactions of four pyridazine derivatives, i.e., 6‐chloro‐3‐hydroxy‐pyridazine, 1,2‐dihydrogen‐1‐methyl‐3,6‐pyridazindione, 6‐chloro‐3‐diethylamino‐ethoxy‐pyridazine, and 1‐methyl‐2‐diethylaminoethyl‐3,6(2H)‐pyridazindione, have been studied using density functional theory (DFT) B3LYP method at the 6‐311+G** basis set. The geometric structures of reactants, transition states and products have been optimized. The transition states have been explored and proved by vibration analysis as well as intrinsic reaction coordination (IRC) analysis. The activation energies of four reactions were calculated, and the corresponding isomerization mechanisms were also elucidated in theory. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 相似文献
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CH2=CHCl与O(3P)反应的理论研究 总被引:1,自引:0,他引:1
用量子化学密度泛函理论和QCISD (Quadratic configuration interaction calculation)方法, 对O(3P)与CH2CHCl的反应进行了理论研究. 在UB3LYP/6-311++G(d,p), UB3LYP/6-31++G(3df, 3pd)计算水平上, 优化了反应物、产物、中间体和过渡态的几何构型, 并在UQCISD(T)/6-311++G(2df,2pd)水平上计算了单点能量. 为了确证过渡态的真实性, 在UB3LYP/6-311++G(3df,3pd)水平上进行了内禀坐标(IRC)计算和频率分析, 并确定了反应机理. 研究结果表明, 反应主要产物为CH2CHO和Cl. 相似文献
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在G3B3, CCSD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p)水平上详细研究了CH3SH与基态NO2的微观反应机理. 在B3LYP/6-311++G(d,p)水平得到了反应势能面上所有反应物、过渡态和产物的优化构型, 通过振动频率分析和内禀反应坐标(IRC)跟踪验证了过渡态与反应物和产物的连接关系. 在CCSD(T)/6-311++G(d,p)和G3B3水平计算了各物种的能量, 得到了反应势能面. 利用经典过渡态理论(TST)与变分过渡态理论(CVT)并结合小曲率隧道效应模型(SCT), 分别计算了在200~3000 K温度范围内的速率常数kTST, kCVT和kCVT/SCT. 研究结果表明, 该反应体系共存在5个反应通道, 其中N进攻巯基上H原子生成CH3S+HNO2的通道活化势垒较低, 为主要反应通道. 动力学数据也表明, 该通道在200~3000 K计算温度范围内占绝对优势, 拟合得到的速率常数表达式为k1CVT/SCT=1.93×10-16T0.21exp(-558.2/T) cm3&;#8226;molecule-1&;#8226;s-1. 相似文献
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IntroductionThe nitro derivatives of methylbenzene are an important category of explosives, in whichTNT (2, 4, 6--trinitrotoluene) is widely--used. It is widely accepted that methyl hydrogen in m....troaromatlcs is quite active, which influences the impact sensitivity of an explosive. Gonzalezet al. [IJ found methyl substitution increases the decomposition rate over that of nitrobenzeneby an order of magnitude. Much effort has been devoted to relating electronic structure and.....impact sens… 相似文献
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在B3LYP/6-311++G(d,p)水平上研究了HOSO+NO的反应机理. 优化得到了反应势能面上各驻点的几何构型, 通过内禀反应坐标(IRC)确认了反应物、中间体、过渡态和产物的相关性. 在CCSD(T)/6-311++G(d,p)水平上对计算得到的构型进行了能量校正. 应用经典过渡态理论(TST)与变分过渡态理论(CVT), 并结合小曲率隧道(SCT)效应模型校正的方法计算了标题反应在200-3000 K温度范围内的速率常数kTST、kCVT和kCVT/SCT. 计算结果表明: HOSO+NO反应在单重态和三重态条件下均可发生, 其中单重态反应为主反应通道, HNO+SO2为主产物. 并利用电子密度拓扑分析方法研究主反应通道反应过程中的化学键变化. 相似文献
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Avramov PV Adamovic I Ho KM Wang CZ Lu WC Gordon MS 《The journal of physical chemistry. A》2005,109(28):6294-6302
The reaction paths for formation and isomerization of a set of silica SimOn (m = 2,3, n = 1-5) nanoclusters have been investigated using second-order perturbation theory (MP2) with the 6-31G(d) basis set. The MP2/6-31G(d) calculations have predicted singlet ground states for all clusters excluding Si3O2. The total energies of the most important points on the potential energy surfaces (PES) have been determined using the completely renormalized (CR) singles and doubles coupled cluster method including perturbative triples, CR-CCSD(T) with the cc-pVTZ basis set. Although transition states have been located for many isomerization reactions, only for Si3O3 and Si3O4 have some transition states been found for the formation of a cluster from the separated reactants. In all other cases, the process of formation of SimOn clusters appears to proceed without potential energy barriers. 相似文献
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Addition reactions of carbon-centered radicals to unsaturated compounds have been studied using quantum chemistry. Following the review by Fischer and Radom (Angew. Chem., Int. Ed. 2001, 40, 1340.), the radicals were grouped in four different families, and the alkenes were selected from among those typical of polymer productions. All of the kinetic constants were calculated using density functional theory and classic transition state theory. Geometries of reactants, products, and transition states were determined at the B3LYP/6-311+G(d,p) level of theory, whereas reaction enthalpies, activation energies, and kinetic constants were estimated using different basis sets. By comparative evaluation of the results obtained with different basis sets, the best computational approach for each kinetic step was identified. As a result of this study, a computational methodology suitable for investigating a large number of kinetic pathways typical of free-radical polymerization processes is proposed. 相似文献
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CH3(2A′)自由基与臭氧反应机理的量子化学研究 总被引:2,自引:0,他引:2
用量子化学UMP2方法,在6-311++G**基组水平上研究了CH3(2A′)自由基与臭氧反应机理,全参数优化了反应过程中反应物、中间体、过渡态和产物的几何构型,在UQCISD(T)/6-311++G**水平上计算了它们的能量;并对它们进行了振动分析,以确定中间体和过渡态的真实性;同时应用经典过渡态理论计算了反应的速率常数,并与实验值进行了比较, CH3自由基与臭氧反应速率常数的理论计算结果为: 4.73×10-14 cm3•molecule-1•s-1,与实验报导的结果(k=2.52×10-14 cm3•molecule-1•s-1)很接近,同时发现CH3(2A′)自由基与O3的反应是强放热反应. 相似文献
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用密度泛函理论(DFT)中的B3LYP方法,采取6-31+G* *基组对2-氨基-5巯基-1,3,4-噻二唑(简称AMT)的异构化反应机理进行了量子化学研究,全参数优化了异构化过程中反应物、产物的几何构型,找出了异构化途径中的过渡态,并通过振动分析加以确认,同时进行零点能校正.研究结果表明,异构化过程存在六种不同的异构化通道,有六个过渡态,相对而言, A→C之间的异构化反应最易发生,C是最稳定的异构化产物. 相似文献