Experimental and Theoretical Study of Hydrogen Atom Abstraction from Ethylene by Stoichiometric Zirconium Oxide Clusters

使用配有团簇产生和化学反应源的飞行时间质谱装置,研究了锆氧阳离子团簇Zr_xO_y⁺和乙烯的反应. 在这个反应中,发现了产物(ZrO₂)_xH⁺ (x=1～4). 使用密度泛函理论研究了乙烯在Zr₂O₄⁺上的反应通道,发现除了通常的氧转移反应外,乙烯脱氢反应也可以发生,从而支持观察到的产物(ZrO_{2相似文献}   

CuC3H-团簇阴离子与CO反应：H辅助的C-C偶联

本研究利用质谱和密度泛函理论计算研究了CuC₃H^-团簇阴离子与CO的反应. 实验结果指出CO与团簇CuC₃H^-中的C₃H^-部分偶联可生成唯一产物COC₃H^-. 此反应的活性和选择性远高于团簇CuC₃^-与CO的反应. 理论计算结果进一步明确了H辅助的C-C偶联反应.     

锰氧化物团簇正离子与硫化氢反应的实验与理论研究 (cited: 2)

采用激光溅射法制备了同位素标记的氧化锰团簇正离子Mn_m¹⁸O_n⁺,并研究了其在快速流动反应管中与硫化氢在热碰撞条件下的反应,氧化锰团簇正离子与硫化氢反应前后的质量分布与强度变化由飞行时间质谱仪检测．实验表明,绝大多数氧化锰团簇正离子可与硫化氢发生氧-硫交换反应产生水分子,反应通式为：Mn_m¹⁸O_n⁺+H₂S→Mn_m¹⁸O_n-1S⁺+H₂¹⁸O．通过密度泛函理论计算了氧化锰团簇正离Mn₂O₂⁺、Mn₂O₃⁺和Mn₂O₄⁺与H₂S反应的机理,结果显示,在这些反应体系中氧-硫交换反应通道同时具有热力学和动力学优势,印证了实验中观察到的现象．气相团簇研究发现的氧-硫交换反应与相关凝聚相体系反应结果一致     

小尺寸VmOn+团簇的激光光解和密度泛函计算

通过激光溅射法产生了V₂O_n⁺ (n=1, 2), V₃O_n⁺ (n=1, 2, 3)和V₄O₃⁺等缺氧的钒氧团簇,并采用532和266 nm波长的激光对它们进行了光解研究. 利用密度泛函理论计算与激光光解实验相结合确定了这些团簇的几何结构和可能的光解通道. 激光光解实验表明V相似文献   

O-与CH3CN反应机理的密度泛函理论研究

采用G3MP2B3方法研究了氧负离子与乙腈反应的势能剖面.在(U)B3LYP/6-31+G(d,p)理论水平下分别优化了该反应势能面上反应物、产物、中间体和过渡态的分子结构,采用G3MP2B3方法校正了这些关键点的能量. 势能面上的各个反应路径均通过针对过渡态的內禀反应坐标理论计算加以确定. 分别考察了四个可能的热力学产物通道,即质子转移、氢原子转移、H₂⁺转移和双分子亲核取代反应途径. 其中,经H₂⁺转移生成H₂O的反应通道为该反应的主要产物通道.     

用于团簇负离子的共线光电子速度成像仪

描述了包含共线的光电子速度成像仪,以及与双阀激光溅射团簇源联用的时间飞行质谱装置．为了避免预混气体,两个脉冲阀和一个反应通道被用来产生反应负离子．共线的光电子成像仪采用了改进的速度成像透镜系统,它的能量分辨率优于3%．此外还报道了Si₄^-团簇在532和355 nm,以及Si₃C^- 团簇在532 nm的光电子速度成像．从实验图像中可以获得光电子能谱和各向异性参数．从Si₄^-团簇能谱上获得了中性的Si₄团簇的基态和第一激发态的振动频率分别为330和312 cm^-1．初步的实验结果证明这套光电子成像装置对研究团簇负离子的电子结构以及光脱附动力学非常有效.     

VxOyq团簇按照△=2y+q-5x值进行分类

按照团簇的氧化指数,对钒氧化物团簇V_xO_y^q (x≤8, q=0,±1)进行了分类(钒氧化物的氧化指数△=2y+q-5x). 密度泛函理论计算结果表明,氧化指数相同的团簇倾向于具有相似的成键方式、电子结构和反应活性. 根据这一规律,提出了V₂O₆和V₃O₆⁺新的可能的基态构型. 在钒氧化物体系上的成功应用,表明这种分类方法可以有效地     

第一性原理计算ZrnFe(n=2—13)团簇的基态结构及其磁性

从第一性原理出发，利用密度泛函理论中的广义梯度近似对Zr_nFe(n=2—13)团簇进行了结构优化、能量和频率计算.在充分考虑自旋多重度的前提下，对每一具体尺寸的团簇，得到了多个平衡构型，并根据能量高低确定了团簇的基态结构.综合团簇的结合能、二阶能量差分以及团簇的最高占据轨道和最低未占据轨道间的能隙可知Zr₅Fe，Zr₇Fe和Zr₁₂Fe团簇的稳定性相对较高，Zr₁₂Fe团簇的结构是具有I_h对称性的正二十面体，而且Zr₁₂Fe的稳定性在所有团簇中是最高的.另外，不仅Zr₅Fe，Zr₇Fe和Zr₁₂Fe团簇的稳定性相对较高，而且它们均为磁性团簇(而Zr_n团簇的磁矩在n≥5时已经发生了淬灭)，由此可知通过选择合适的掺杂元素可能得到高稳定的磁性团簇.从Mulliken布居分析结果可知，除了在Zr₁₂Fe团簇中Fe原子失去少量电荷外，其他团簇中Fe原子均从Zr原子那里得到了一定量电荷，即Fe原子在Zr_nFe(n=2—13，n≠12)团簇中是电子受体.     

基于从头算势能面对S-(2P)+H2(1Σ+g)→SH-(1Σ)+H(2S)反应的量子含时波包计算

本文基于离子分子SH₂^-基态势能面,应用含时波包方法研究了反应S^-(²P)+H₂(¹Σ⁺_g)→SH^-(¹Σ)+H(²S)的动力学行为. 给出了反应几率和积分截面随碰撞能的变化关系,结果表明,在讨论的所有碰撞能量范围内二者均存在显著的振荡结构. 当初始转动量子数j=0,2,4,6,8,10和振动量子数v=0,1,2,3,4时,从总反应几率数值计算中可以看出,双原子H₂的振动激发和转动激发显著提高了反应活性. 同时积分散射截面的理论值与前人的实验值相符合.     

Superacid Catalyst SO42-/ZrO2-La2O3 Prepared by Ultrasonic Co-precipitation and Low Temperature Aging

低温陈化超声波共沉淀法制得SO₄^2-/ZrO^2-La₂O₃前驱体, 经H₂SO₄处理, 在不同温度下焙烧得到纳米晶催化剂SO₄^2-/ZrO^2-La₂O₃;用Hammett指示剂法测定其酸性. 用XRD、BET、TEM、IR和XPS对样品进行表征,其催化活性用醋酸和甘油的酯化反应进行了评价. 结果表明经超声波搅拌和低温(-15 ºC)陈化,650 ºC焙烧4 h得到的固体超强酸表现出较高催化活性.     

50—5000 eV电子被C4H8O,C5H10O2, C6H5CH3和C4H8O2散射的总截面

使用电子被C, H和O原子散射总截面的实验数据, 利用修正后的可加性规则计算了能量为50—5000eV的电子被4个复杂大分子C₄H₈O, C₅H₁₀O₂, C₆H₅CH₃和C₄H₈O₂散射的总截面, 并将计算结果与实验结果及其他理论计算结果进行了比较. 结果表明, 即 关键词： 电子散射 可加性规则 总截面 几何屏蔽效应     

The influence of structural defects on the adsorption of simple molecules (H2, C2H2, C2H4, C2H6, CO,NO) on rhenium single crystals

Using Thermal Programmed Desorption (TPD), Low Energy Electron Diffraction (LEED) and Auger Electron Spectroscopy (AES) we have studied the adsorption of hydrogen-containing molecules (H₂, C₂H₂, C₂H₄, C₂H₆) and oxygen-containing molecules (CO and NO) on two vicinal planes of the Re(0001) surface. The two surfaces are designated thus: ReS ¦14(0001)(101̄1)¦, ReS |6(0001)(167̄1) | . The structural defects have little effect on the adsorption of hydrogen and the hydrocarbons. They are more influential in the case of the oxygen-containing molecules. This is particularly true for CO; on the kink sites the CO molecules can completely dissociate whereas only a partial dissociation is possible on the steps. These results should be viewed in relation to the strong bond energy between carbon and oxygen in a CO molecule of 256 kcal/mole and the great affinity of oxygen for rhenium; E_Re?O = 127 kcal/mole.     

Adsorption of CO and C2H4 on Rh-loaded thin-film dysprosium oxide

A dysprosium oxide thin film was deposited on Ru(0 0 0 1) by vapor depositing Dy in 2 × 10⁻⁷ torr O₂ while the Ru was at 700 K. The film was ca. 5 nm thick and produced a p(1.4 × 1.4) LEED pattern relative to the Ru(0 0 0 1) substrate. The adsorption and reaction of CO and C₂H₄ adsorbed on Rh supported on the Dy₂O₃ film were studied by TPD and SXPS. The CO initially reacted with loosely bound oxygen in the substrate to produce CO₂. After the loosely bound oxygen was removed, the CO adsorbed non-dissociatively in a manner similar to what is seen on Rh(1 1 1). C₂H₄ adsorbed on the Rh particles and underwent progressive dehydrogenation to produce H₂ during TPD. The C from the C₂H₄ reacted with the O in Dy₂O₃ to produce CO. CO dissociation on the Rh particles could be promoted by treating the Dy₂O₃ with C₂H₄ before CO exposure.     

Temperature and pressure effects on formation and decomposition of phenylvinylperoxy radicals in the C6H5C2H2 + O2 reaction

The effects of temperature and pressure on the formation and decomposition of C₆H₅C₂H₂O₂ in the C₆H₅C₂H₂ + O₂ reaction have been investigated at temperatures from 298 to 378 K by directly monitoring the C₆H₅C₂H₂O₂ radical in the visible region by cavity ringdown spectrometry (CRDS). The rate constant for the C₆H₅C₂H₂ + O₂ association and that for fragmentation of C₆H₅C₂H₂O₂ were found to be k₁ (C₆H₅C₂H₂ + O₂ → C₆H₅C₂H₂O₂) = (3.20 ± 1.19) × 10¹¹ exp(+760/T) cm³ mol⁻¹ s⁻¹ and k₂ (C₆H₅C₂H₂ O₂ → C₆H₅CHO + HCO) = (1.68 ± 0.13) × 10⁴ s⁻¹, respectively. Additional kinetic measurements by pulsed laser photolysis/mass spectrometry show that C₆H₅CHO was produced in the C₆H₅C₂H₂ + O₂ reaction as predicted and the formation of C₆H₅CHO from the decomposition of C₆H₅C₂H₂O₂ is temperature-independent, consistent with the CRDS experimental data.     

Auger spectra of CO,C2H4, C2N2 and C6H6 adsorbed on Pt(111)

Electron excited carbon KVV Auger spectra of CO, C₂H₄, C₂N₂ and C₆H₆ adsorbed on Pt(111) are compared. By estimating the effective Coulomb interaction between the final-state holes it is possible to associate some features with transitions observed in free molecule spectra, but others must involve at least one electron with energy within the conduction band of the metal. Such “cross-transitions” are associated with strong 2π* character of filled states in the presence of a core hole in molecules such as CO.     

On the formation and decomposition of C7H8

The kinetics of reactions on the C₇H₈ surface were studied with state-of-the-art ab initio transition state theory (TST) and master equation methodologies. A priori predictions of the capture rate for C₆H₅ + CH₃ and for C₇H₇ + H are obtained from direct variable reaction coordinate TST simulations. These simulations employ small basis set CASPT2 interaction energies coupled with one-dimensional reaction path corrections based on higher level simulations for related reactions. For the C₇H₇ + H reaction, predictions are obtained for both the total rate and for the branching between toluene, o-isotoluene and p-isotoluene. A mapping of the low energy pathways for isomerization from these three C₇H₈ isomers identifies a number of processes with barriers at or below the dissociation threshold. Nevertheless, at combustion temperatures the dissociation rates are predicted to exceed the isomerization rates, and it is reasonable to treat the kinetics of each isomer as a simple single well association/dissociation equilibrium. Master equation simulations yield predictions for the temperature and pressure dependence of each of the recombination and dissociation processes, as well as for the C₇H₇ + H → C₆H₅ + CH₃ bimolecular reaction. These simulations implement collisional energy transfer probabilities based on the work of Luther and co-workers. The theoretical predictions are found to be in satisfactory agreement with the available experimental data for the photodissociation of toluene, the temperature and pressure dependent dissociation of toluene, and the reaction of benzyl radical with H. For the C₆H₅ + CH₃ recombination, the theoretical predictions exceed the experimental measurements of Lin and coworkers by a factor of 2 or more for all temperatures.     

Microwave substitution structure of the amine group in Ortho-chloroaniline,C6H4CINH2

The microwave spectra of amine deuterated species of [2-³⁵Cl] and [2-³⁷-Cl]aniline, C₆H₄ClNH₂, have been observed. The rotators associated with the first two states of the amino group inversion have been assigned. A geometric structure has been calculated from the moments of inertia of all isotopic species in the ground state, indicating a small out-of-plane angle (34.5°), and a torsion around the CN bond of the NH₂ group. This deformation is explained by the formation of a hydrogen bond NH … Cl.     

闭壳层金掺杂钛氧团簇阴离子解离氢分子研究

Dissociation of molecular hydrogen (H₂) is extensively studied to understand the mechanism of hydrogenation reactions. In this study, H₂ dissociation by Au₁-doped closed-shell titanium oxide cluster anions AuTi₃O₇^- and AuTi₃O₈^- has been identified by mass spectrometry and quantum chemistry calculations. The clusters were generated by laser ablation and massselected to react with H₂ in an ion trap reactor. In the reaction of AuTi₃O₈^- with H₂, the ion pair Au⁺-O₂^2- rather than Au⁺-O^2- is the active site to promote H₂ dissociation. This finding is in contrast with the previous result that the lattice oxygen is usually the reactive oxygen species in H₂ dissociation. The higher reactivity of the peroxide species is further supported by frontier molecular orbital analysis. This study provides new insights into gold catalysis involving H₂ activation and dissociation.     

Thermal stability of cubane C8H8

The reasons for the anomalously high thermal stability of cubane C₈H₈ and the mechanisms of its decomposition are studied by numerically simulating the dynamics of this metastable cluster at T = 1050–2000 K using a tight-binding potential. The decomposition activation energy is found from the temperature dependence of the cubane lifetime obtained from the numerical experiment; this energy is fairly high, E _a = 1.9 ± 0.1 eV. The decomposition products are, as a rule, either C₆H₆ and C₂H₂ molecules or the isomer C₈H₈ with a lower energy. Original Russian Text ? M.M. Maslov, D.A. Lobanov, A.I. Podlivaev, L.A. Openov, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 3, pp. 609–612.     

Microwave substitution structure of the amine group in meta-chloroaniline C6H4CINH2

Microwave spectra of amine-deuterated species of 3-³⁵Cl-aniline, C₆H₄CINH₂, have been observed. The two amino hydrogen atoms are found to be out of the plane of the aromatic ring, and appear to be farther out of the plane when the amine group is deuterated. It has also been shown that the H_trans, c coordinate (0.300 Å) is larger than the cis one (0.281 Å).