Communication: state-to-state quantum dynamics study of the OH + CO → H + CO2 reaction in full dimensions (J = 0)

A full dimensional state-to-state quantum dynamics study is carried out for the prototypical complex-formation OH + CO → H + CO(2) reaction in the ground rovibrational initial state on the Lakin-Troya-Schatz-Harding potential energy surface by using the reactant-product decoupling method. With three heavy atoms and deep wells on the reaction path, the reaction represents a huge challenge for accurate quantum dynamics study. This state-to-state calculation is the first such a study on a four-atom reaction other than the H(2) + OH ? H(2)O + H and its isotope analogies. The product CO(2) vibrational and rotational state distributions, and product energy partitioning information are presented for ground initial rovibrational state with the total angular momentum J = 0.     

Quantum dynamics of the S+OH→SO+H reaction

First accurate quantum mechanical scattering calculations have been carried out for the S((3)P)+OH(X?(2)Π)→SO(X?(3)Σ(-))+H((2)S) reaction using a recent ab initio potential energy surface for the ground electronic state, X?(2)A("), of HSO. Total and state-to-state reaction probabilities for a total angular momentum J=0 have been determined for collision energies up to 0.5 eV. A rate constant has been calculated by means of the J-shifting approach in the 10-400 K temperature range. Vibrational and rotational product distributions show no specific behavior and are consistent with a mixture of direct and indirect reaction mechanisms.     

超临界CO2+CH3OH及C2H5OH二元系的气液平衡

在带有石英可视窗和内搅拌的可变体积高压釜内，测定了超临界CO2＋CH3OH及C2H5OH两个系统的相平衡数据，温度为50－200℃，压力4．0－16．0MPa，利用从硬球模型得出的适用于高压高温的状态方程，计算了这两个系统的临界曲线，并与实验值进行比较。     

OH自由基与CO反应的研究

用时间分辨-傅立叶变换红外发射光谱法研究了OH自由基与CO的反应.OH自由基由248 nm的激光光解硝酸得到.在实验中首次观测到了产物CO2的非对称伸缩振动(ν3)的激发态.对CO2发射光谱的拟合结果显示,其振动态的布居在量子数v=2时最大 ,而最高振动量子数达到v=6.由实验得到的CO2振动布居与Schatz等人用全量子化计算该反应的中间物HOCO解离动力学得到的CO2布居结果能很好地吻合.     

C02+OH2/C03+OH2电子转移反应性的理论研究

提出了研究Co2+OH2/Co3+OH2反应体系电子转移反应性的接触距离依赖关系的分析方案和ab initio计算的应用方法,并讨论验证了此方案及其相应模型的可行性,分析了有关动力学量的接触距离依赖关系.详细的结果表明,用精确PES法得出的活化能与用非谐振子势得出的活化能吻合较好,它们明显优于谐势模型.对分布函数随接触距离从1.20～0.35 nm改变而从10-2变到10-5.偶合矩阵元随接触距离的增加呈指数性降低.有效电子偶合要求接触距离＜0.75 nm.在0.50～0.75 nm范围内,相应的电子发射系数值在1.0～10-6之间.电子因子使得定域ET速率也指数性的随接触距离的增加而降低,而对分布函数对总电子转移速率的贡献与电子因子的贡献则相反.球平均ET速率随接触距离的变化呈抛物线变化,并在接触距离为0.5 nm时有最大值.此最大值与总观测ET速率非常接近.对于此偶合体系,气态时ET速率是106 L@mol-1@s-1.进一步来说,实验上难于确定此类水合体系尤其是未饱和中间组分的电子结构和PES,abinitio算法在讨论其ET反应性方面能起到一个有效的辅助作用.     

Theoretical study on the reaction mechanism of(CH_3)_3CO+CO

The global environment pollution includes pho-tochemical smog, acid rain and stratospheric ozonedepletion. The short-lived species/radicals in atmos-phere are closely related to these phenomena. Theshort-lived species/radicals bring the photochemicalsmog,…     

ESR研究CO,CH_3OH,HCHO和CO+H_2等体系在MgO新鲜表面上的反应

氧化镁经机械粉碎后,形成具有高活性中心的新鲜表面。将一氧化碳、甲醛、甲醇分别吸附在氧化镁新鲜表面上,用ESR分别检测到CO_2~-,(CH_2O~-)(ads),和(CH_2~-)(ads)等负离子自由基的信号。而CO+H_2在氧化镁新鲜表面上反应形成了顺磁性的中间态,当温度升至573K时,该吸附态转变成两种新的吸附态:一种是甲醇形式的吸附态(OCH_2~-)(ads),该吸附态在温度大于643K时发生脱附;另一种是甲醛形式的吸附态(CH_2—O~-),该吸附态在温度大于823K时才脱附。最后,提出了CO+H_2在氧化镁新鲜表面上反应的可能机理。     

What are the Implications of Nonequilibrium in the O+OH and O+HO2 Reactions?

Vibrationally excited O2, OH, and HO2 species have been suggested (J. Phys. Chem. A 2004, 108, 758) to provide clues for explaining the "ozone deficit problem" and "HOx dilemma" in the middle atmosphere under conditions of local thermodynamic disequilibrium (LTD), but the question arises of how much LTD will affect the title ozone sink reactions. Besides providing novel kinetic results, it is shown that LTD tends to disfavor ozone depletion relative to traditional atmospheric modeling under Boltzmann equilibration, which is partly due to competition between the various reactive channels. The calculations also suggest that the title LTD processes can be important sources of highly vibrationally excited O2 in the middle atmosphere. Moreover, LTD is shown to offer an explanation for the fact that some down revision of the O + HO2 rate constant, or the ratio of the O + HO2 to O + OH rate constants, is required to improve agreement between the predictions of traditional modeling and observation. This, in turn, provides significant evidence supporting LTD at such altitudes.     

OH+C2H2与OH+C2H4加成反应的热力学和动力学

OH基与乙炔(乙烯)的反应是控制大气中OH基浓度的重要化学反应。对反应OH+C_2H_2,1975年Davis等用FP-RF技术测定了反应的速率常数。1977年,Perry又用同样方法对该反应作出了研究;结果表明,此反应的速率常数强烈地依赖于压力,与Davis等人的实验结果不符。对反应OH+C_2H_4,Atkinson等人的实验研究表明,压力在30.0kPa以下,反应的速率常数随压力而改变;而在30.0—88.4 kPa之间,与压力无关.这与前人的结果不同。两个反应的产物也因温度不同而异.此外,上述反应一般是在近101kPa下发生的,而实验结果大多是在低压下获得的。且目前尚无直接的理论计算结果。为此,我们在从头算水平上用统计热力学方法,对反应     

Mechanistic and kinetic study of CF3CH═CH2 + OH reaction

The potential energy surfaces of the CF(3)CH═CH(2) + OH reaction have been investigated at the BMC-CCSD level based on the geometric parameters optimized at the MP2/6-311++G(d,p) level. Various possible H (or F)-abstraction and addition/elimination pathways are considered. Temperature- and pressure-dependent rate constants have been determined using Rice-Ramsperger-Kassel-Marcus theory with tunneling correction. It is shown that IM1 (CF(3)CHCH(2)OH) and IM2 (CF(3)CHOHCH(2)) formed by collisional stabilization are major products at 100 Torr pressure of Ar and in the temperature range of T < 700 K (at P = 700 Torr with N(2) as bath gas, T ≤ 900 K), whereas CH(2)═CHOH and CF(3) produced by the addition/elimination pathway are the dominant end products at 700-2000 K. The production of CF(3)CHCH and CF(3)CCH(2) produced by hydrogen abstractions become important at T ≥ 2000 K. The calculated results are in good agreement with available experimental data. The present theoretical study is helpful for the understanding the characteristics of the reaction of CF(3)CH═CH(2) + OH.     

HNCO+OH→H2O+NCO的反应机理

采用从头算分子轨道法(UHF/6-31G**水平,并用MP4加以相关能校正)研究了HNCO+OH→H2O+NCO反应机理.同时用Morokuma数值法获得了反应途径即内禀反应坐标(IRC).沿着IRC,运用反应途径哈密顿理论,获得反应途径动态学信息.在此基础上,根据过渡态理论和相应隧道效应校正,计算了在不同温度下的反应速率常数,得到了和实验相一致的结果.计算结果表明,此反应是一步直接型的抽提H反应.     

Radiative lifetime of CO+ (X2∑+, ν) ions

The radiative relaxation of CO⁺(X²∑⁺, ν) ions produced by ionization of CO and of OCS with 70 eV electrons has been investigated using the monitor ion technique in a triple FT ICR spectrometer. Since the monitor reaction is exothermic for ν ≥ 1, the experimental lifetimes, 170 ms for CO⁺ from CO and 210 ms for CO⁺ from OCS, should correspond to the overall decay rate of ν ≥ 2 with a small contribution of ν = 1.These values being much larger than the theoretical lifetime of ν = 1 (128.5 ms), computer-simulated overall lifetimes for ν ≥ 1 and ν ≥ 2 have been determined using theoretical lifetimes calculated by Rosmus and Werner and a vibrational population deduced from photoelectron spectroscopy of CO with 40.8 eV photons (Gardner and Samson). The computer-simulated lifetimes, 250 ms for ν ≥ 1 and 125 ms for ν ≥ 2, are indeed about twice as large as the theoretical lifetimes for ν = 1 and ν = 2, respectively, indicating that the large experimental lifetimes may be accounted for by radiative cascade from the upper vibrational levels.     

A restricted active space (RAS) SCF study of the lifetime of theA 3Π state of OH+

Summary Restricted Active Space (RAS) SCF calculations have been performed of the potential curves for theX ^3– andA ³ states of the OH⁺ ion and on the lifetime of thev=0–2 vibrational levels of theA state. The convergence of the transition moment integral as a function of the size of the active orbital space was used to select the active orbitals. The calculated value of thev=0 lifetime is 2.4 µs. An estimate of the errors remaining in the calculation leads to a final theoretical value of 2.7±0.1 µs. Computed bond distances and bond energies are 1.031 (1.029) Å and 5.05 (5.01) eV, respectively, for theX state, and 1.137 (1.135) Å and 1.57 eV, respectively, for theA state (experimental values within parenthesis).On leave from Departamento de Quimica Fisica, Universitat de València, Dr. Moliner 50, Burjassot, 46 100 València, Spain     

Quasi-classical trajectory study of the H + CO2 → HO + CO reaction on a new ab initio based potential energy surface

A detailed quasi-classical trajectory study of the H + CO(2) → HO + CO reaction is reported on an accurate potential energy surface based on ab initio data. The influence of the vibrational and rotational excitations of CO(2) was investigated up to the collision energy of 2.35 eV. It was found that the total reaction integral cross section increases monotonically with the collision energy, consistent with experimental results. The excitation of the CO(2) bending vibration enhances the reaction, while the excitation in its asymmetric stretching vibration inhibits the reaction. The calculated thermal rate constants are in excellent agreement with experiment. At the state-to-state level, the rotational state distributions of the HO product are in good agreement with experimental results, while those for the CO product are much hotter than measurements. The calculated differential cross sections are dominated by forward scattering, suggesting that the lifetime of the HOCO intermediate may not be sufficiently long to render the reaction completely statistical.     

Quasi-classical trajectory study of the HO + CO → H + CO2 reaction on a new ab initio based potential energy surface

We report extensive quasi-classical trajectory calculations of the HO + CO → H + CO(2) reaction on a newly developed potential energy surface based on a large number of UCCSD(T)-F12/AVTZ calculations. This complex-forming reaction is known for its unusual kinetics and dynamics because of its unique potential energy surface, which is dominated by the HOCO wells flanked by an entrance channel bottleneck and a transition state leading to the H + CO(2) products. It was found that the thermal rate coefficients are in reasonably good agreement with known experimental data in both low and high pressure limits. Excitation of the OH vibration is shown to enhance reactivity, due apparently to its promoting effect over the transition state between the HOCO intermediate and the H + CO(2) product. On the other hand, neither CO vibrational excitation nor rotational excitation in either CO or OH has a significant effect on reactivity, in agreement with experiment. However, significant discrepancies have been found between theory and the available molecular beam experiments. For example, the calculated translational energy distribution of the products substantially underestimates the experiment. In addition, the forward bias in the differential cross section observed in the experiment was not reproduced theoretically. While the origin of the discrepancies is still not clear, it is argued that a quantum mechanical treatment of the dynamics might be needed.     

Nonadiabatic quantum reactive scattering of the OH(A 2Σ+) + D2

The seams of conical intersection exist between the ground (1 (2)A(')) and the first-excited (2 (2)A(')) electronic potential energy surfaces (PESs) of OH(A (2)Σ(+),X (2)Π) + H(2) system. This intersection induces the nonadiabatic quenching of OH(A (2)Σ(+)) by D(2). We present nonadiabatic quantum dynamics study for OH(A (2)Σ(+)) + D(2) on new five-dimensional coplanar PESs. The ab initio calculations of PESs are based on multireference configuration interaction (MRCI)/aug-cc-pVQZ level. A back-propagation neural network is utilized to fit the PESs and nonadiabatic coupling. High degrees of rotational excitation of quenched OH(X (2)Π) products are found in nonreactive quenching channel, and the quenched D(2) products are vibrationally excited up to quantum number v(2) (')=8. The theoretical results of nonadiabatic time-dependent wave-packet calculation are in good agreement with the existing experimental data.     

The study on the effect of the substitution of K2CO3 with Ca(OH)2 on kinetics on CO2–lignite coal gasification

Research on Chemical Intermediates - Three kinds of lignite were mixed with K2CO3 and Ca(OH)2 and were gasified with CO2 to investigate the effect that the addition of Ca(OH)2 had on the...     

CO…CO+ 体系相互作用的密度泛函理论研究

在三种密度泛函方法(B3LYP、B3P86及B3PW91)和两种适宜基组(6-311+G*及aug-cc-PVDZ)水平上,对CO…CO+耦合体系可能存在的相互作用复合物进行了全自由度能量梯度优化,发现势能面上存在三个能量极小点,进而作了振动频率分析加以确认.其中结构A、 B为共平面型结构, C为非共面型结构. 比较了它们之间的相对稳定性,并对其进行了轨道成键分析,计算了各原子之间的键级,同时探讨了最稳定结构A的正则振动模式. 通过消除基函数引起的基组叠加误差(BSSE)和零点振动能(ZPVE)的校正,精确求算出复合物结构A、 B和C的相互作用能△E分别为252.47、 126.70和127.12 kJ/mol, 表明CO和CO+之间存在较强的相互作用.