反应N+NH→N2+H的态-态量子动力学研究

采用在MRCI/aug-cc-pVQZ水平上构建的N₂H基态势能面, 并运用Chebyshev实波包法研究了N + NH→N₂ + H反应的量子动力学, 如反应几率、 积分截面以及产物振转态分布等. 在50~500 K温度范围内, 该反应的速率常数随着温度升高而递增, 与基于其它势能面的理论结果吻合. 然而, 在室温条件下, 所有理论计算的速率常数均显著大于实验值.     

Accurate Quantum Dynamics of the Simplest Isomerization System Involving Double-H Transfer

We perform accurate quantum dynamics calculations on the isomerization of vinylidene-acetylene. Large-scale parallel computations are accomplished by an efficient theoretical scheme developed by our group, in which the basis functions are customized for the double-H transfer process. The \begin{document}$ A_1' $\end{document} and \begin{document}$ B_2'' $\end{document} vinylidene and delocalization states are obtained. The peaks recently observed in the cryo-SEVI spectra are analyzed, and very good agreement for the energy levels is achieved between theory and experiment. The discrepancies of energy levels between our calculations and recent experimental cryo-SEVI spectra are of similar magnitudes to the experimental error bars, or \begin{document}$ \le $\end{document}30 cm\begin{document}$ ^{-1} $\end{document} excluding those involving the excitation of the CCH\begin{document}$ _2 $\end{document} scissor mode. A kind of special state, called the isomerization state, is revealed and reported, which is characterized by large probability densities in both vinylidene and acetylene regions. In addition, several states dominated by vinylidene character are reported for the first time. The present work would contribute to the understanding of the double-H transfer.     

HNCS与CH2(X2Π)反应微观动力学的理论研究

用量子化学密度泛函理论的UB3LYP/6-311+G**方法和高级电子相关的UQCISD(T)/6-311+G**方法研究了异硫氰酸(HNCS)与乙炔基自由基(C2H(X2Π))反应的微观机理. 采用双水平直接动力学方法IVTST-M, 获取反应的势能面信息, 应用正则变分过渡态理论并考虑小曲率隧道效应, 计算了在250～2500 K温度范围内反应的速率常数. 研究结果表明, HNCS与C2H(X2Π)反应为多通道、多步骤的复杂反应, 共存在三个可能的反应通道, 主反应通道为通过分子间H原子迁移, 生成主要产物NCS+C2H2. 反应速率常数随温度升高而增大, 表现为正温度效应. 速率常数计算中变分效果很小. 在低温区隧道效应对反应速率的贡献较大, 反应为放热反应.     

反应Si+HCl→SiCl+H的直接动力学研究

利用从头算直接动力学方法，研究反应Si HCl→SiCl H的动力学性能，在QCISD／6－311＋G（d,p)和CCSD（T）／aug-cc-pvtz(单点）水平上，得到体系的势能面信息，进而利用变分过渡态理论计算了反应的速率常数及其与温度的关系。计算结果与实验符合得很好。     

D+HCN反应的SVRT含时波包理论研究

基于Horst的势能面,用SVRT(SemirigidVibratingRotorTarget)方法对D+HCN反应进行了含时波包动力学研究,计算得到了不同初始振转态的总反应几率和积分反应截面,采用UniformJ-shifting方法得到该反应的热速率常数.计算结果与H+HCN反应进行了比和讨论.     

单壁碳纳米管内受限溶剂中振动光谱探针的混合量子-经典动力学模拟

利用混合量子-经典动力学模拟方法, 考察了不同管径的单壁碳纳米管(SWCT)中受限溶剂氩的径向分布以及溶质I2分子的振动弛豫动力学, 给出了I2分子的振动频率位移、振动弛豫时间随受限碳纳米管管径尺寸变化的关系. 以I2分子的振动频率位移为探针, 根据I2分子与周围环境作用的实时信息, 分析了管壁、受限溶剂对光谱探针的贡献, 在原子、分子层次上揭示了诱导频率位移的微观机制; 此外, 通过分析探针光谱的敏感性以及探针分子频率位移与振动弛豫时间的关系, 进一步阐明了振动频率位移是考察受限凝聚相中分子间相互作用的较好的探针.     

Theoretical Investigations on Photodissociation Dynamics of Deuterated Alkyl Halides CD3CH2F

The product branching ratio between different products in multichannel reactions is as important as the overall rate of reaction, both in terms of practical applications (\emph{e.g}. models of combustion or atmosphere chemistry) in understanding the fundamental mechanisms of such chemical reactions. A global ground state potential energy surface for the dissociation reaction of deuterated alkyl halide CD\begin{document}$ _3 $\end{document}CH\begin{document}$ _2 $\end{document}F was computed at the CCSD(T)/CBS//B3LYP/aug-cc-pVDZ level of theory for all species. The decomposition of CD\begin{document}$ _3 $\end{document}CH\begin{document}$ _2 $\end{document}F is controversial concerning C\begin{document}$ - $\end{document}F bond dissociation reaction and molecular (HF, DF, H\begin{document}$ _2 $\end{document}, D\begin{document}$ _2 $\end{document}, HD) elimination reaction. Rice-Ramsperger-Kassel-Marcus (RRKM) calculations were applied to compute the rate constants for individual reaction steps and the relative product branching ratios for the dissociation products were calculated using the steady-state approach. At the different energies studied, the RRKM method predicts that the main channel for DF or HF elimination from 1, 2-elimination of CD\begin{document}$ _3 $\end{document}CH\begin{document}$ _2 $\end{document}F is through a four-center transition state, whereas D\begin{document}$ _2 $\end{document} or H\begin{document}$ _2 $\end{document} elimination from 1, 1-elimination of CD\begin{document}$ _3 $\end{document}CH\begin{document}$ _2 $\end{document}F occurs through a direct three-center elimination. At 266, 248, and 193 nm photodissociation, the main product CD\begin{document}$ _2 $\end{document}CH\begin{document}$ _2 $\end{document}+DF branching ratios are computed to be 96.57%, 91.47%, and 48.52%, respectively; however, at 157 nm photodissociation, the product branching ratio is computed to be 16.11%. Based on these transition state structures and energies, the following photodissociation mechanisms are suggested: at 266, 248, 193 nm, CD\begin{document}$ _3 $\end{document}CH\begin{document}$ _2 $\end{document}F\begin{document}$ \rightarrow $\end{document}absorption of a photon\begin{document}$ \rightarrow $\end{document}TS5\begin{document}$ \rightarrow $\end{document}the formation of the major product CD\begin{document}$ _2 $\end{document}CH\begin{document}$ _2 $\end{document}+DF; at 157 nm, CD\begin{document}$ _3 $\end{document}CH\begin{document}$ _2 $\end{document}F\begin{document}$ \rightarrow $\end{document}absorption of a photon\begin{document}$ \rightarrow $\end{document}D/F interchange of TS1\begin{document}$ \rightarrow $\end{document}CDH\begin{document}$ _2 $\end{document}CDF\begin{document}$ \rightarrow $\end{document}H/F interchange of TS2\begin{document}$ \rightarrow $\end{document}CHD\begin{document}$ _2 $\end{document}CHDF\begin{document}$ \rightarrow $\end{document}the formation of the major product CHD\begin{document}$ _2 $\end{document}+CHDF.     

双分子水和氨气催化CF3OH分子裂解的理论研究

The G3 and CBS-QB3 theoretical methods are employed to study the decomposition of CF₃OH into FCFO and HF by water, water dimmer, and ammonia. The decomposition of CF₃OH into FCFO and HF is unlikely to occur in the atmosphere due to the high activated energy of 88.7 kJ/mol at the G3 level of theory. However, the computed results predict that the barrier for unimolecular decomposition of CF₃OH is decreased to 25.1 kJ/mol from 188.7 kJ/mol with the aid of NH₃ at the G3 level of theory, which shows that the ammonia play a strong catalytic effect on the split of CF₃OH. In addition, the calculated rate constants show that the decomposition of CF₃OH by NH₃ is faster than those of H₂O and the water dimmer by 109 and 105 times respectively. The rate constants combined with the corresponding concentrations of these species demonstrate that the reaction CF₃OH with NH₃ via TS4 is of great importance for the decomposition of CF₃OH in the atmosphere.     

Path Integral Liouville Dynamics Simulations of Vibrational Spectra of Formaldehyde and Hydrogen Peroxide

Formaldehyde and hydrogen peroxide are two important realistic molecules in atmospheric chemistry. We implement path integral Liouville dynamics (PILD) to calculate the dipole-derivative autocorrelation function for obtaining the infrared spectrum. In comparison to exact vibrational frequencies, PILD faithfully captures most nuclear quantum effects in vibrational dynamics as temperature changes and as the isotopic substitution occurs.     

离子液体的量化计算及分子动力学模拟研究进展

离子液体是由有机阳离子和无机/有机阴离子构成的盐类,一般在室温或接近于室温下呈液态,因此常被称为室温离子液体(RTIL).依据不同的划分标准,离子液体有多种分类方式:根据年代的不同可将离子液体分为第一代、第二代及第三代离子液体,例如:烷基咪唑和烷基吡啶的金属卤化物盐等[1];根据阳离子的不同可将离子液体分为季鏻     

二极管激光探测法研究高振动NO2与NH3振动传能

用高分辨、高速、高灵敏度的二极管激光探测法研究了高振动激发的NO2分子与NH3分子的振动能量转移，YAG532um倍频光作为NO2的激发光源，红外二极管激光（约10μ）探测NH3ν2模被激发振转能级的时间分辨的吸收光谱.实验得到NO2与NH3气压比为1：5，1：1，2：1和5：1时NH3（0100；7；k）的激发速率分别为9．28、6．42、5．05和3．65×10－1ms－1·Pa－1.在NH3压力为133Pa时，有大约6％的高振动激发NO2能量转移到NH3ν2振动模，其它大部分转移到NH3的转动和平动能．文中讨论了振动激发的机理．     

Analytical solution of the master equation with the transition probability derived from dynamical considerations

An exact relationship between the transition probability P(E → E^′) and quantum transition probabilities P_i→f of an active molecule under the effect of collisions with medium molecules is obtained. Treating an active molecule as a system of harmonic oscillators, it is possible to derive the analytical expression for P(E → E^′) from the “first principles” using the first-order perturbation theory for probabilities P_i→f. The only parameter of the model is expressed in terms of vibrational relaxation time that may be calculated numerically or taken from experiments. For the system of harmonic oscillators placed in a thermal bath, the solution of the master equation is found in the analytical form. An extended discussion of the model is also presented.     

振动和转动激发对N2在Fe(111)表面解离吸附的影响(英文)

N₂的解离化学吸附是工业合成氨的速控步骤.基于最近构建的六维势能面,本文研究了N₂的初始振动激发和转动激发在Fe(111)表面的反应性的作用.由于该反应具有重要的量子效应,通过六维量子动力学计算研究了入射能量低于1.6 eV时振动激发的效应.并采用准经典轨线计算揭示了高入射能量下的振动和转动激发的影响.通过这些研究发现增加平动能量在一定程度上能提高解离几率,振动激发或转动激发能更有效地促进解离.这项研究为重原子分子-表面反应的模式特异性动力学提供了有价值的见解.     

溶液环境中CdSeS量子点与金纳米颗粒相互作用

选用不同发射波长的合金型CdSeS量子点(QDs), 研究溶液状态下量子点和金纳米颗粒(AuNPs)相互作用及离子强度、pH值、距离等诸多因素对相互作用的影响, 在此基础上对相互作用的机理进行了分析. 在溶液状态下, 金纳米颗粒可以高效地淬灭量子点, Stern-Volmer 淬灭常数K_sv值在108 L·mol^-1数量级. 这种淬灭效应与距离、光谱之间叠合程度等密切相关, 受溶液极性、离子强度、pH值的影响较小. 金纳米颗粒与量子点相互作用的机理较为复杂, 以能量转移为主. 研究结果对设计更高效的生物传感器及更全面认识金纳米颗粒与量子点相互作用的机理具有重要意义.     

噻吩低聚物能级结构的量子化学研究

用量子化学方法计算了系列EDOT低聚物的紫外-可见吸收光谱和前线分子轨道,得到了相应的能级结构参数.与实验值进行对比发现,计算值与实验值具有相同的变化趋势.计算结果表明,通过选择性地改变共轭主链的长度、取代基的位置和取代基的类型,可以规律性地改变化合物光谱性质和能级结构.     

碳离子碰撞单壁碳纳米管的动力学

采用分子动力学方法研究了碳离子碰撞碳纳米管中顶位、键中心和六元环中心的动力学过程。通过分析低、中、高3种入射能分别对碰撞过程的影响,探索了典型缺陷形成的微观演化过程。研究结果表明,碰撞碳纳米管中不同空间位置,其碰撞结果差异较大,其中顶位碰撞阈能最低,约为20 eV;碰撞六元环中心时碳管会发生严重变形,损伤最为严重。通过分析入射离子动能,碳纳米管热动能、质心动能以及势能随时间的演化规律,阐述了碰撞过程中的能量转移机制。     

碳离子碰撞单壁碳纳米管的动力学

采用分子动力学方法研究了碳离子碰撞碳纳米管中顶位、键中心和六元环中心的动力学过程。通过分析低、中、高3种入射能分别对碰撞过程的影响,探索了典型缺陷形成的微观演化过程。研究结果表明,碰撞碳纳米管中不同空间位置,其碰撞结果差异较大,其中顶位碰撞阈能最低,约为20 e V;碰撞六元环中心时碳管会发生严重变形,损伤最为严重。通过分析入射离子动能,碳纳米管热动能、质心动能以及势能随时间的演化规律,阐述了碰撞过程中的能量转移机制。     

D＋CH4反应的SVRT含时波包理论研究

基于Jordan和Gilbert势能面,用SVRT(semirigid vibrating rotor target)模型,对D＋CH4反应进行了含时波包动力学研究,计算得到了不同初始振动转动态的总反应几率、积分散射截面和热速率常数.计算结果与H＋CH4反应进行了比较和讨论.反应几率随平动能的变化曲线呈现出显著的量子共振特性.通过对j=0时,v=0、1、2的反应几率的计算,看出H－CH3的振动激发极大地提高了反应几率,而反应阈能明显降低,说明反应分子的振动能对分子的碰撞反应有重要贡献.对v=0时,j=0、1、2、3的反应几率的计算,得出转动量子数j的增大也会使反应几率有较大的提高,但反应阈能基本不变.     

分子动力学模拟纳米尺寸限制体系下氩溶液中I2的振动能量弛豫

利用平衡态分子动力学方法(EMD)模拟了纳米尺寸限制球壳内I2在Ar溶液中的振动能量转移. 计算并讨论了I2振动能量弛豫时间T1随球壳半径、溶剂密度的变化规律. 通过分子间相互作用分析, 在原子、分子水平上, 揭示了随着球壳半径的减小, T1呈逐渐增大趋势的原因. 结果表明, 球壳的几何限制效应和表面作用对受限溶液密度分布的影响较大, 从而导致溶质振动弛豫的显著变化. 此外, 非限制体系模拟显示, 非平衡态分子动力学(NEMD)方法可以得到与平衡态分子动力学方法较一致的振动能量弛豫时间T1.     

HCN + OH→CN + H2O反应理论研究

The reaction path of the reaction HCN + OH→ CN + H2O was traced with Fukui's theory of intrinsic reaction coordinate by using ab initio MO method (at UMP4/6-31G** level) with gradient technique. On this basis, the dynamics properties along the reaction path was investigated by reaction path Hamiltonian theory. The rate constants of this reaction at different temperatures were calculated by conventional and variational transition state theory with tunneling correction. The theoretically calculated rate constants are in good agreement with experimental results, this shows that the title reaction is an one step, direct reaction.