Transport numbers of H+ and O2- in the electrochemical system (H2 + H2O),Me/BaCe0.9Nd0.1O3-α/Me,(H2 + H2O)

In the temperature range 873–1123 K, transport numbers of oxygen ions and protons are determined in the system (H₂ + H₂O), Me/BaCe_0.9Nd_0.1O_3-α/Me,(H₂ + H₂O), where Me = Ag, Au, Pt, Ni, by the emf and current methods. The determined transport numbers are independent of the determination method, the electrode material, the current direction (anodic and cathodic polarization of the electrode), polarizability of electrodes, and the partial water (hydrogen) pressure in the gas phase. This unambiguously suggests that the transport numbers refer to the solid electrolyte, and not the electrochemical system as a whole. It also follows that partial currents of the hydrogen ionization and the oxygen ion discharge are determined by the transport numbers of protons and oxygen ions in the electrolyte. At a constant temperature, their ratio is affected by neither the electrode potential nor the gas phase composition, i.e., both electrode reactions have a common limiting step (or steps). Deceased.     

·C2H3+O2→HC·O+H2CO 的密度泛函理论研究

应用密度泛函理论研究了@C2H3+O2→HC@O+H2CO的反应机理.在DFT(B3LYP/6-31G*)水平上对反应过程中所有反应物、中间体、过渡态和产物的几何构型进行优化,通过频率振动分析确认中间体和过渡态.计算IRC反应路径的能量,分析了中间体的异构化过程和各主要原子的自旋密度.     

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.     

Rate constants of atomic hydrogen formation in H3O+(H2O) n + e → H + (H2O) n gas-phase processes

Using the Maxwellian electron velocity distribution and the Breit-Wigner approximation of the reaction cross section, the kinetic parameters of the hydrogen atom formation upon the electron capture by positively charged hydronium-water clusters are estimated. Calculations of the cross sections and rate constants are based on the data of quantum chemical studies of H₃O⁺(H₂O) _n and H₃O(H₂O) _n clusters, particularly on the detailed analysis of the spacing of high-lying states of the radicals and the character of the unpaired electron density distribution, as well as on the general trend in the electron affinity change of the cations depending on the number of water molecules. The lifetimes of the radicals before the dissociation are taken from the classical nonempirical molecular dynamics runs. The results are compared to available experimental data. The article is published in the original.     

BH2+与H2O反应机理的量子拓扑研究

采用密度泛函方法B3LYP/6-311+G(d, p)和耦合簇方法CCSD/6-311+G(d, p)研究了BH2+与H2O的气相离子-分子反应机理. 优化得到了反应途径中各驻点的几何构型, 并采用内禀反应坐标法进行追踪. 从量子拓扑学的角度, 讨论了在反应过程中各化学键的变化. 反应(I)经历了一个四元环过渡态, 找到了这个反应的能量过渡态和两个结构过渡态.     

CH2O+H→CHO+H2反应途径和变分速率常数计算研究

采用QCISD/6-311G^** 从头算方法,优化了吸氢反应CH2O+H→CHO+H2的反应物、过渡态、产物几何结构,得出该反应的正、逆反应活化位垒分别是35.4kJ/mol和98.8kJ/mol。沿IRC分析指出该反应是一个C—H键断裂和H—H键生成协同进行的反应,而且在反应途径上存在一个引导反应进行的振动模式,这一反应模式引导反应进行的区间在—0.4～0.55(amu)^1/2之间。在300～3200K温度范围内,运用变分过渡态理论(CVT),计算了该反应的速率常数。     

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.     

Pitzer model parameters for sparingly soluble salts from solubility measurements. The systems TlCl+SrCl2+H2O and TlCl+BaCl2+H2O at 25°C

The solubility of thallium(I) chloride has been determined in aqueous solutions of strontium chloride and barium chloride at concentrations up to 1.5 mol kg^–1. The data were analyzed using Pitzer's equations without making explicit assumption of association to ion pairs by assuming =3 instead of =2, with the ⁽¹⁾ term for TlCl being equivalent to the ⁽²⁾ term for 2-2 electrolytes. Best values of ⁽⁰⁾ and ⁽¹⁾ for TlCl are recommended together with K _s , the activity solubility product. These were used to fit the present solubility data and derive the Pitzer model mixture parameters relevant to the systems, _fTIN and _fTINCl (N=Sr, Ba). Mixture parameters for TlCl+MCl+H₂O systems are also derived to complete the parameter base. The fit of the experimental data was found to be worse when higher-order terms for asymmetrical mixing were included in the analysis. Activity coefficients for thallium(I) chloride in the mixtures are derived.     

Lack of salt effect on the kinetics of the reaction SO2−4 + H3O+ → HSO−4 + H2O

It is found that the broadening of the 1100-cm⁻¹ line of SO⁻²₄, caused by increasing [H₃O⁺], is unaffected by addition of 4 M LiCl, NaBr, KCl and NH₄Cl. This finding is in line with the lack of influence of NaCl reported earlier. The significance of these findings, in terms of the reaction mechanism, is discussed.     

An analysis of the vibrational frequencies and amplitudes of the H5O+2 ion in H4SiW12O40·6H2O (TSA·6H2O) and H3PW12O40·6H2O (TPA·6H2O)

The infrared, Raman and inelastic neutron scattering (INS) spectra of TSA·6H₂O and TPA·6H₂O are in agreement with those expected for the presence of H₅O⁺₂ ions. Force fields for different assignment schemes are compared with the observed vibrational frequencies and the INS spectral profile. All but two schemes are eliminated. Whilst low-resolution INS spectroscopy cannot distinguish between these two schemes, the orientations of the vibrational ellipsoids for one scheme are in better agreement with those reported from low-temperature crystallographic studies of the H₅O⁺₂ ion.     

A theoretical study of the H2SO4+H2O → HSO4 −+H3O+ reaction at the surface of aqueous aerosols

The surface region of sulfate aerosols (supercooled aqueous concentrated sulfuric acid solutions) is the likely site of a number of important heterogeneous reactions in various locations in the atmosphere, but the surface region ionic composition is not known. As a first step in exploring this issue, the first acid ionization reaction for sulfuric acid, H₂SO₄ + H₂O HSO₄^– + H₃O⁺, is studied via electronic structure calculations at the Hartree–Fock level on an H₂SO₄ molecule embedded in the surface region of a cluster containing 33 water molecules. An initial H₂SO₄ configuration is selected which could produce H₃O⁺ readily available for heterogeneous reactions, but which involves reduced solvation and is consistent with no dangling OH bonds for H₂SO₄. It is found that at 0 K and with zero-point energy included, the proton transfer is endothermic by 3.4 kcal/mol. This result is discussed in the context of reactions on sulfate aerosol surfaces and, further, more complex calculations.Contribution to the Jacopo Tomasi Honorary Issue     

Ab initio reaction rate constants computed using semiclassical transition-state theory: HO + H2 → H2O + H and isotopologues

A new algorithm [Nguyen, T. L.; Stanton, J. F.; Barker, J. R. Chem. Phys. Lett. 2010, 9, 499] for the semiclassical transition-state theory (SCTST) formulated by W. H. Miller and co-workers is used to compute rate constants for the isotopologues of the title reaction, with no empirical adjustments. The SCTST and relevant results from second-order vibrational perturbation theory (VPT2) are summarized. VPT2 is used at the CCSD(T) level of electronic structure theory to compute the anharmonicities of the fully coupled vibrational modes (including the reaction coordinate) of the transition structure. The anharmonicities are used in SCTST to compute the rate constants over the temperature range from 200 to 2500 K. The computed rate constants are compared to experimental data and theoretical calculations from the literature. The SCTST results for absolute rate constants and for both primary and secondary isotope effects are in excellent agreement with the experimental data for this reaction over the entire temperature range. The sensitivity of SCTST to various parameters is investigated by using a set of simplified models. The results show that multidimensional tunneling along the curved reaction path is important at low temperatures and the anharmonic coupling among the vibrational modes is important at high temperatures. The theoretical kinetics data are also presented as fitted empirical algebraic expressions.     

基态H2O+的全域多体势能面

基态H₂O⁺分子离子是重要的星际反应中间体.用MRCISD/cc-pVTZ先计算H₂O⁺势能面,然后拟合成多体势能函数.全域势能面能很好地描述基态H₂O⁺的行为.与两条反应通道的实验能变和其构型翻转反应能垒比较,表明计算结果与实验值相符.对计算点完成了力场的多项式拟合,对其振动模式进行了分析     

A priori rate constant for the reaction NH2+NO → N2+H2O

Capture rates for a dipole-dipole+Morse potential, from approximate semiclassical trajectory calculations, have been combined with RRKM rates for passing through entropy bottlenecks on the potential surface for NH₂ + NO → N₂ + H₂O. The resulting overall rate constants are in good agreement with experiment. The effective lifetime of the NH₂NO collision complex is found to be of the order of 10⁻¹¹s at room temperature, which accounts for the observed lack of pressure dependence of the rate constant. Calculated rate constants increase markedly at low temperatures, though not as rapidly as some of the experimental data would indicate.     

Spectral studies on Ag8+ ions irradiated LAHCl·H2O and LAHBr·H2O single crystals

L-arginine hydrochloride monohydrate and L-arginine hydrobromide monohydrate single crystals are irradiated by 100 MeV Ag8+ swift heavy ions. The residual gases liberated from the irradiated samples are monitored as a function of ion fluence using quadrupole mass analyzer. The C2H3+, C2H2, N2, CO, HCl and CO2 are the dominant gases liberated. Fourier transform infrared spectra of irradiated crystals explain the breaking of bonds in a localized region of the crystals. The crystallinity of irradiated crystals is analyzed by powder X-ray diffractions.     

H3+O和H3+O(H2O)n(n=1,2,3)阳离子振动力场和光谱频率的理论计算

本文利用多原子分子振动力场的模型势函法对H₃⁺O和H₃⁺O(H₂O)_n(n=1～3)阳离子的振动力场作了理论计算,并对其光谱频率进行了预测.H₃⁺O和H₉⁺O₄的振动频率的结果优于从头算梯度法的结果.本文首次给出了H₅⁺O₂、H₇⁺O₃伸缩振动频率的理论预测值.     

H+O2(n0, j0)→HO+O及C+H2(n0, j0)→CH+H体系选态反应截面的过渡态理论计算

本文用微正则过渡态理论计算了H+O_2(n_0,j_0)→HO+O和C+H_2(n_0, j_0)→CH+H在ab initio势能面上的选态反应截面σ_(n_0,j_0); E.分析了势能面性质对反应截面的影响。计算结果表明, 在指定反应物分子的振动态n_0、转动态j_0时, 两个反应体系的反应截面随相对平动能的增加先是增加后是减小(j_0=1, n_0=0除外); 在给定相对平动能和反应物分子的转动态j_0时, 随反应物分子的振动量子数n_0的增加, 两个体系的选态反应截面均有较显著的增加, 在指定相对平动能和反应物分子的振动态n_0时, H+O_2体系的选态反应截面随j_0的变化较为复杂, 而C+H_2体系则比较简单(j_0=1除外)。对于H+O_2反应体系, 本文得到的反应截面与实验结果及准经典轨迹理论的计算结果符合得很好。     

O(3P)+O2H→OH+O2反应机理的密度泛函理论研究

用密度泛函理论方法研究了O(3P)与O2H反应生成羟基和氧分子的反应机理. 在PW91/6-31+G水平上用梯度解析技术全自由度优化上述反应物、产物和反应路径上的中间体及过渡态几何构型, 并通过频率振动分析加以确认, 计算IRC反应路径及中间体异构化过程, 确定了此反应的可能反应通道. 结果表明: 该反应是多通道多步骤的强放热反应. 首先形成顺式或反式O3H富能中间体, 此过程无能垒; 然后跨过一个能垒分解成产物OH和O2. 通道IM1→TS1比IM2→TS2克服的能垒要大, 反应放热372.822 kJ*mol-1. IM1TS3IM2 可相互转化.