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Hydrogen Abstraction from Fluorinated Ethyl Methyl Ether Systems by OH Radicals OH自由基从氟化乙基甲基醚体系中提取氢
Pub Date : 2016-02-10 DOI: 10.1155/2016/3740278
Curtis White, Jaime M. Martell
A systematic computational investigation of hydrogen abstraction by OH from the full series of fluorinated ethyl methyl ethers (EME) containing at least one H and one F, (, ; and not allowed), including 147 reactants and 469 transition states, has been carried out, employing the MP2/6-31G(d) level of theory. Results for optimized geometries, including evidence of intramolecular hydrogen bonding in transition states, and barrier heights are presented. Trends pertaining to the number of fluorines substituted, key bond lengths, barrier heights, and key bond angles were found with good correlations and were investigated. An increase in the number of F increases the barrier height of the reaction. An increase in some parameters such as C–H length of TS, relative change in C–H from reactants to TS, ∠COC of reactants, ∠HOH in the TS, and relative change in ∠HOH between TS and free water bond angle also correlates with increased barrier height. An increase in other parameters like C–H length in the reactants and hydrogen bonding can decrease the barrier height.
从含有至少一个H和一个F的全系列氟化乙基甲基醚(EME)中OH提取氢的系统计算研究,(,;和不允许),包括147个反应物和469个过渡态,采用MP2/6-31G(d)水平的理论进行。优化几何结构的结果,包括过渡态分子内氢键和势垒高度的证据。发现与取代的氟数、键长、势垒高度和键角有关的趋势具有良好的相关性,并对其进行了研究。F数目的增加使反应的势垒高度增加。TS的C-H长度、反应物到TS的C-H相对变化、反应物的∠COC、TS中的∠HOH、TS与自由水键角之间的∠HOH的相对变化等参数的增加也与势垒高度的增加有关。其他参数如反应物C-H长度和氢键的增加可以降低势垒高度。
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引用次数: 3
A Group Theoretical and Quantum Chemical Study of Electronic Absorption and Fluorescence, Vibrational Spectra, and Conformations of Trimethine Cyanine Dye Molecules 三甲基菁染料分子的电子吸收、荧光、振动光谱和构象的群理论和量子化学研究
Pub Date : 2016-01-18 DOI: 10.1155/2016/6737494
V. V. Solomko, P. Kondratenko, Y. Lopatkin
The energetic structures and conformations of trimethine cyanine dye molecules were investigated. For research, group theoretical and quantum chemical calculation methods were used. The theoretical group analysis of electronic and vibrational structure of molecules was carried out. Also, the energetic structures and conformations of the molecule of this dye were studied. Research shows that the investigated molecule may reside in three different conformational states, one of which is highly symmetric (symmetry ) and the other two with low symmetry. The third conformer is characterized by lowering of binding energy of the electronic system by 0.23 eV, and the long-wavelength absorption band is shifted to lower energies. Also the group theoretical analysis of the trimethine cyanine molecule had allowed systematizing the vibrational and electronic quantum transitions and identifying the bands in the absorption spectra. It is shown that the excitation of the molecule in -state causes trans-cis-isomerization. The presence of the barrier of ~0.1 eV allows the fluorescence process to compete with isomerization process, but isomerization causes a decrease in the fluorescence quantum yield of the dye.
研究了三甲基菁染料分子的能量结构和构象。研究采用了群理论和量子化学计算方法。对分子的电子结构和振动结构进行了理论群分析。并对染料分子的能量结构和构象进行了研究。研究表明,所研究的分子可能存在三种不同的构象状态,其中一种是高度对称的(对称),另两种是低对称的。第三种构象的特点是使电子系统的结合能降低了0.23 eV,长波长吸收带向较低能量转移。此外,对三甲基花青素分子的基团理论分析使其振动和电子量子跃迁变得系统化,并确定了吸收光谱中的能带。结果表明,激活处于态的分子可引起反式顺式异构化。~0.1 eV势垒的存在使得荧光过程可以与异构化过程竞争,但异构化会导致染料的荧光量子产率下降。
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引用次数: 0
Decay of Metastable State with Account of Agglomeration and Relaxation Processes 考虑团聚和弛豫过程的亚稳态衰减
Pub Date : 2016-01-05 DOI: 10.1155/2016/9468050
V. Kurasov
Theoretical description of the metastable phase decay kinetics in the presence of specific connections between the embryos of small sizes has been given. The theory of the decay kinetics in the presence of relaxation processes is constructed in analytical manner. The -mers nucleation is investigated and the global kinetics of decay is also constructed in this case analytically.
在小尺寸胚胎之间存在特定连接的情况下,给出了亚稳相衰变动力学的理论描述。用解析的方法建立了存在弛豫过程的衰变动力学理论。在这种情况下,研究了-mers的成核过程,并建立了整体衰变动力学。
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引用次数: 0
DFT Study of a Novel Organic Film: The Structural versus Magnetic Effects 一种新型有机薄膜的DFT研究:结构与磁效应
Pub Date : 2015-11-29 DOI: 10.1155/2015/597584
S. Simonetti, A. Juan, G. Brizuela, S. Ulacco
Unsaturated fatty acids have great interest by their activities as industrial materials in novel applications. In the present work, the cis-3-hexenoic acid (HA) adsorbed on the Ni(111) surface was studied by first-principles calculations using the Vienna Ab Initio Simulation Package (VASP). The most stable location for HA is presented on top site of Ni(111), although the energies are very similar for all the adsorption sites. The surface-molecule interaction takes place between the carboxyl group of HA and surrounding Ni atoms. The adsorption is weak and consequently the metal-molecule length is enhanced. The carboxyl group is elongated and weakened after adsorption giving rise to a shift in stretching frequencies. There are notable changes on the magnetic moments values of Ni surface atoms neighboring to the molecule that mainly induced magnetic moments on O and H atoms. Noticeable charge transfer occurs in 3d 4s, p Ni orbitals and 2s C, 2s p O, 1s H orbitals of carboxyl group. The surface presents positive work function changes after adsorption as a consequence of an electron back-donation. During interaction, the significance of the magnetic effects over the structural effects is evidenced. This sets the stage for a future adsorption process improvement based on the modification of the surface magnetic properties.
不饱和脂肪酸因其作为工业原料的新用途而受到广泛关注。在本工作中,利用维也纳从头算模拟程序包(VASP)对Ni(111)表面吸附的顺式-3-己烯酸(HA)进行了第一性原理计算研究。HA最稳定的位置出现在Ni(111)的顶部位置,尽管所有吸附位点的能量非常相似。表面分子相互作用发生在HA的羧基和周围的Ni原子之间。吸附较弱,金属分子长度增大。羧基在吸附后被拉长和削弱,从而引起拉伸频率的变化。与分子相邻的Ni表面原子的磁矩值发生了显著的变化,主要诱导了O和H原子的磁矩。羧基的第3个4s、p Ni轨道和第2个C、2s p O、1s H轨道发生了明显的电荷转移。由于电子回给,吸附后表面呈现正功函数变化。在相互作用过程中,证明了磁效应对结构效应的重要性。这为未来基于改性表面磁性的吸附工艺改进奠定了基础。
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引用次数: 1
Geometry, Energy, and Some Electronic Properties of Carbon Polyprismanes: Ab Initio and Tight-Binding Study 碳多棱镜的几何、能量和一些电子性质:从头算和紧密结合研究
Pub Date : 2015-10-26 DOI: 10.1155/2015/506894
K. Katin, S. A. Shostachenko, A. I. Avkhadieva, M. Maslov
We report geometry, energy, and some electronic properties of [n,4]- and [n,5]prismanes (polyprismanes): a special type of carbon nanotubes constructed from dehydrogenated cycloalkane C4- and C5-rings, respectively. Binding energies, interatomic bonds, and the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) have been calculated using density functional approach and nonorthogonal tight-binding model for the systems up to thirty layers. It is found that polyprismanes become more thermodynamically stable as their effective length increases. Moreover, they may possess semiconducting properties in the bulk limit.
我们报道了[n,4]-和[n,5]棱柱烷(聚棱柱烷)的几何、能量和一些电子性质:一种特殊类型的碳纳米管,分别由脱氢的环烷烃C4-和c5环构成。利用密度函数法和非正交紧密结合模型,计算了30层以下体系的结合能、原子间键和最高已占据分子轨道(HOMO)与最低未占据分子轨道(LUMO)之间的能隙。研究发现,随着聚合物有效长度的增加,聚合物的热力学稳定性提高。此外,它们在体积范围内可能具有半导体性质。
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引用次数: 20
DFT Study on the Oxidative Addition of 4-Substituted Iodobenzenes on Pd(0)-Phosphine Complexes Pd(0)-膦配合物上4-取代碘苯氧化加成的DFT研究
Pub Date : 2015-10-04 DOI: 10.1155/2015/985268
Tímea R. Kégl, L. Kollár, T. Kégl
The oxidative addition of 4-substituted iodobenzenes on Pd(0)-PMe3 complexes has been studied at the BP86 level of theory including dispersion correction and solvation effect, with tetrahydrofuran as solvent. The bisphosphine pathway was found to be barrierless, whereas the monophosphine route is hampered by the high dissociation energy of trimethylphosphine. The reaction free energy of this step shows linear correlation with the Hammett constants of the para substituents with the most electron withdrawing groups being the most exergonic.
以四氢呋喃为溶剂,在BP86水平上研究了Pd(0)-PMe3配合物上4-取代碘苯的氧化加成反应,包括分散性校正和溶剂化效应。双膦途径被发现是无障碍的,而单膦途径被三甲基膦的高解离能所阻碍。这一步的反应自由能与对取代基的哈米特常数呈线性相关,其中吸电子最多的基团是最易溶的。
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引用次数: 7
Revisiting Oxidative Dehydrogenation of Ethane by W Doping into MoVMn Mixed Oxides at Low Temperature 低温掺杂钨锰混合氧化物乙烷氧化脱氢研究
Pub Date : 2015-01-27 DOI: 10.1155/2015/102583
Mohammed H. Al-Hazmi, T. Odedairo, Adel S. Al-Dossari, YongMan Choi
The catalytic performance of MoVMnW mixed oxides was investigated in the oxidative dehydrogenation of ethane at three different reaction temperatures (235, 255, and 275°C) using oxygen as an oxidant. The catalysts were characterized by using X-ray diffraction, temperature-programmed reduction, and scanning electron microscopy. The MoVMnW mixed oxide catalyst showed the 70–90% of ethylene selectivity at the reaction temperatures. However, a significant decrease in the selectivity of ethylene was observed by increasing the reaction temperature from 235°C to 275°C.
以氧为氧化剂,研究了MoVMnW混合氧化物在235、255和275℃三种不同反应温度下对乙烷氧化脱氢的催化性能。采用x射线衍射、程序升温还原和扫描电镜对催化剂进行了表征。在反应温度下,MoVMnW混合氧化物催化剂的乙烯选择性为70 ~ 90%。然而,当反应温度从235℃升高到275℃时,乙烯的选择性明显降低。
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引用次数: 0
Preparation of Zirconium Oxide Powder Using Zirconium Carboxylate Precursors 用羧酸锆前驱体制备氧化锆粉体
Pub Date : 2014-12-31 DOI: 10.1155/2014/429751
Mohammed H. Al-Hazmi, YongMan Choi, A. Apblett
Zirconia was prepared at low temperatures (<450°C) using single several source precursors based on zirconium carboxylates where the R groups were systematically varied. The combination of density functional theory (DFT) calculations and extensive characterization of the precursors (i.e., X-ray diffraction, thermal gravimetric analysis, infrared spectroscopy, and scanning electron microscopy) indicated that the carboxylic acid complexes may link the zirconium metal with a cis bidentate configuration. Periodic DFT calculations were performed to examine the interaction between monoclinic ZrO2 and propanoic acid. Dissociative adsorption takes place through the cis bidentate structure with an adsorption energy of −1.43 eV. Calculated vibrational frequencies using the optimized structure are in good agreement with experimental findings.
在低温(<450°C)条件下,以羧酸锆为原料制备氧化锆,其中R基团是系统变化的。结合密度泛函理论(DFT)计算和前驱体的广泛表征(即x射线衍射、热重分析、红外光谱和扫描电镜)表明,羧酸配合物可能以顺式双齿构型连接金属锆。通过周期性DFT计算,考察了单斜ZrO2与丙酸之间的相互作用。通过顺式双齿结构进行解离吸附,吸附能为- 1.43 eV。采用优化结构计算得到的振动频率与实验结果吻合较好。
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引用次数: 10
Adsorption of Polyanion onto Large Alpha Alumina Beads with Variably Charged Surface 具有可变电荷表面的大α -氧化铝珠对聚阴离子的吸附
Pub Date : 2014-12-15 DOI: 10.1155/2014/460942
T. Pham, Motoyoshi Kobayashi, Y. Adachi
Adsorption of strong polyelectrolyte, poly(styrenesulfonate), PSS, of different molecular weights onto large α-Al2O3 beads was systematically investigated as functions of pH and NaCl concentrations. The ultraviolet (UV) absorption spectra of PSS at different pH and salt concentrations confirmed that the structure of PSS is independent of pH. With the change of molecular weight from 70 kg/mol (PSS 70) to 1000 kg/mol (PSS 1000), adsorption amount of PSS increases and proton coadsorption on the surface of α-Al2O3 decreases at given pH and salt concentration. It suggests that higher molecular weight of PSS was less flat conformation than lower one. The adsorption density of PSS 70 and PSS 1000 decreases with decreasing salt concentrations, indicating that both electrostatic and nonelectrostatic interactions are involved. Experimental results of both PSS 70 and PSS 1000 adsorption isotherms onto α-Al2O3 at different pH and salt concentrations can be represented well by two-step adsorption model. The effects of molecular weight and salt concentration are explained by structure of adsorbed PSS onto α-Al2O3. The influence of added SDS on the isotherms is evaluated from the sequential adsorption. The SDS uptake onto α-Al2O3 in the presence of hemimicelles can prevent the adsorption of PSS at low concentration so that adsorption of PSS reduces with preadsorbed SDS.
系统研究了不同分子量的强聚电解质聚苯乙烯磺酸盐PSS在大α-Al2O3微球上的吸附作用及其对pH和NaCl浓度的影响。PSS在不同pH和盐浓度下的紫外吸收光谱证实了PSS的结构与pH无关。在一定的pH和盐浓度下,PSS的分子量从70 kg/mol (PSS 70)增加到1000 kg/mol (PSS 1000), PSS的吸附量增加,α-Al2O3表面的质子共吸附量减少。结果表明,高分子量的PSS比低分子量的PSS具有更低的平面构象。PSS 70和PSS 1000的吸附密度随盐浓度的降低而降低,表明其中既有静电作用,也有非静电作用。两步吸附模型能很好地表征PSS 70和PSS 1000在不同pH和盐浓度下对α-Al2O3的吸附等温线。α-Al2O3吸附的PSS结构可以解释分子量和盐浓度的影响。通过序贯吸附评价了SDS对等温线的影响。半胶束存在时SDS吸附在α-Al2O3上可以阻止PSS在低浓度下的吸附,因此预吸附SDS减少了PSS的吸附。
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引用次数: 33
Evaluation of Density Matrix and Helmholtz Free Energy for Harmonic Oscillator Asymmetric Potential via Feynmans Approach 用费曼方法求谐振子不对称势的密度矩阵和亥姆霍兹自由能
Pub Date : 2014-11-02 DOI: 10.1155/2014/912054
P. Moonsri, A. Hutem
We apply a Feynmans technique for calculation of a canonical density matrix of a single particle under harmonic oscillator asymmetric potential and solving the Bloch equation of the statistical mechanics system. The density matrix and kinetic energy per unit length can be directly evaluated from the solving solutions. From the evaluation, it was found that both of the density matrix and kinetic energy per unit length depended on the parameter of the value of asymmetric potential , the value of axes-shift potential , and temperature (T). Comparison of the Helmholtz free energy was derived by the Feynmans technique and the path-integral method. The results illustrated are slightly different.
我们应用费曼技术计算了单粒子在谐振子不对称势下的正则密度矩阵,并求解了统计力学系统的Bloch方程。密度矩阵和单位长度的动能可由解直接求出。计算结果表明,密度矩阵和单位长度动能均与不对称势、轴移势和温度(T)有关。采用费曼技术和路径积分法对亥姆霍兹自由能进行了比较。所示的结果略有不同。
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引用次数: 2
期刊
Advances in Physical Chemistry
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