The catalytic effects of H2CO3, CH3COOH,HCOOH and H2O on the addition reaction of CH2OO + H2O → CH2(OH)OOH

The addition reaction of CH₂OO + H₂O → CH₂(OH)OOH without and with X (X = H₂CO₃, CH₃COOH and HCOOH) and H₂O was studied at CCSD(T)/6-311+ G(3df,2dp)//B3LYP/6-311+G(2d,2p) level of theory. Our results show that X can catalyse CH₂OO + H₂O → CH₂(OH)OOH reaction both by increasing the number of rings, and by adding the size of the ring in which ring enlargement by COOH moiety of X inserting into CH₂OO···H₂O is favourable one. Water-assisted CH₂OO + H₂O → CH₂(OH)OOH can occur by H₂O moiety of (H₂O)₂ or the whole (H₂O)₂ forming cyclic structure with CH₂OO, where the latter form is more favourable. Because the concentration of H₂CO₃ is unknown, the influence of CH₃COOH, HCOOH and H₂O were calculated within 0–30 km altitude of the Earth's atmosphere. The results calculated within 0–5 km altitude show that H₂O and HCOOH have obvious effect on enhancing the rate with the enhancement factors are, respectively, 62.47%–77.26% and 0.04%–1.76%. Within 5–30 km altitude, HCOOH has obvious effect on enhancing the title rate with the enhancement factor of 2.69%–98.28%. However, compared with the reaction of CH₂OO + HCOOH, the rate of CH₂OO···H₂O + HCOOH is much slower.     

An investigation of paddle wheel Cu2(μ2-O2CCH3)4 for gas molecule adsorptions

Metal organic frameworks (MOFs) have been well-known and extensively researched due to the high storage /good selectivity for gas molecules. Herein, the structures and electron paramagnetic resonance (EPR) spectra for dicopper paddle wheel MOF compound (Cu₂(µ₂-O₂CCH₃)₄ with various gas molecule are theoretically investigated by density functional theory (DFT) calculations. The adsorption energies and isotherms (including pure gas molecules and the mixed ones) are calculated for the gas molecules interacting with the unsaturated Cu₂(µ₂-O₂CCH₃)₄. Both quantities exhibit the roughly consistent orders (e.g. H₂S?>?NH₃?>?CO₂?>?CO?>?H₂O?>?N₂?>?NO?>?H₂ for isotherms and H₂S?>?NH₃?>?N₂?>?CO₂?>?NO?>?H₂O?>?H₂?>?CO for adsorption energies), possibly suggesting that this material may act as a potential adsorbent of these gas molecules. The catalytic property of Cu₂(µ₂-O₂CCH₃)₄ for oxidation of CO and NO into non-toxic molecules and splitting of H₂O into H₂ and O₂ in the solvent condition are uniformly discussed. Simulation of Grand Canonical Monte Carlo (GCMC) in MS 8.0 and calculations in Langmuir model reveal that Cu₂(µ₂-O₂CCH₃)₄ has good selectivity for CH₄ in natural gas (CH₄/CO₂/N₂) and SO₂ in fog (SO₂/NO/NO₂/H₂O/O₂), which would exhibit potential environmentally friendly applications.     

Theoretical study on the reactions of CH3NHNH2 with ground state O(3P) atom and excited state O(1D) atom

The reaction mechanisms of methylhydrazine (CH₃NHNH₂) with O(³P) and O(¹D) atoms have been explored theoretically at the MPW1K/6-311+G(d,p), MP2/6-311+G(d,p), MCG3-MPWPW91 (single-point), and CCSD(T)/cc-pVTZ (single-point) levels. The triplet potential energy surface for the reaction of CH₃NHNH₂ with O(³P) includes seven stable isomers and eight transition states. When the O(³P) atom approaches CH₃NHNH₂, the heavy atoms, namely N and C atoms, are the favourable combining points. O(³P) atom attacking the middle-N atom in CH₃NHNH₂ results in the formation of an energy-rich isomer (CH₃NHONH₂) followed by migration of O(³P) atom from middle-N atom to middle-H atom leading to the product P6 (CH₃NNH₂+OH), which is one of the most favourable routes. The estimated major product CH₃NNH₂ is consistent with the experimental measurements. Reaction of O(¹D) + CH₃NHNH₂ presents different features as compared with O(³P) + CH₃NHNH₂. O(¹D) atom will first insert into C–H2, N1–H4, and N2–H5 bonds barrierlessly to form the three adducts, respectively. There are two most favourable paths for O(¹D) + CH₃NHNH₂. One is that the C–N bond cleavage accompanied by a concerted H shift from O atom to N atom (mid-N) leads to the product P_I (CH₂O + NH₂NH₂), and the other is that the N–N bond rupture along with a concerted H shift from O to N (end-N) forms P_IV (CH₃NH₂ + HNO). The similarities and discrepancies between two reactions are discussed.     

The chemisorption of H2O,HCOOH and CH3COOH on thin amorphous films of Al2O3

Inelastic electron tunneling spectroscopy (IETS) has been used to probe the irreversible chemisorption of H₂O, HCOOH, and CH₃COOH on a thin amorphous film of Al₂O₃. The “clean” Al₂O₃ film was also probed in a similar way. The measurement involves examining the second derivative of the I–V curve for electrons tunneling between the metal electrodes in an AlAl₂O₃Pb junction. When chemisorbed species are present on the Al₂O₃, the second derivative measurement is a representation of vibronic excitations of the chemical bonds in the adspecies, i.e. the tunneling spectra are analogous to IR spectra. A “clean” Al₂O₃ surface is found to possess free OH groups essentially equivalent to a surface exposed to large concentrations of H₂O. Saturation coverages of HCOOH and CH₃COOH yield similar spectra to each other, as expected. However, chemical shifts as well as variations in intensity among the equivalent bonds in the adsorbed HCOOH and CH₃COOH are noted. Tentative assignments are given for the observed peaks, and it is concluded that the acids adsorb as formate and acetate ions on the surface. Tunneling spectra for several submonolayer coverages of HCOOH (θ = 0.03, 0.08, 0.3 and 0.4) have been measured in addition to the spectrum corresponding to saturation coverage. Small shifts in certain vibronic transitions as a function of surface coverage have been noted. The shifts in the peak positions are related to variations in adsorbate-adsorbent and adsorbate-adsorbate interactions, and the variations in relative peak intensity are associated with the orientation of the adsorbed molecules. The kinetics of the chemisorption of HCOOH, i.e. the sticking probability as a function of surface coverage, has also been determined for surface coverages between 0.03 and 0.4 monolayer.     

三甲基镓在Pd(111)表面吸附解离及表面预吸附H和O的影响

利用X-射线光电子能谱（XPS）和程序升温脱附谱（TPD）研究了三甲基镓在Pd（111）表面的吸附和解离行为,并考察了表面预吸附H和O的影响。结果表明,在吸附温度为140 K时,三甲基镓在Pd（111）上主要为解离吸附,此时表面物种为Ga（CH₃）_x （x=1,2,3）和CH_x物种。加热将导致Ga的甲基化合物中的Ga-C键发生分步断裂,在不同温度下产生CH₄和H₂从表面脱附。同时,XPS结果证实了在275~325 K的温度区间内存在Ga甲基化合物的分子脱附。退火至更高温度,表面只观察到积碳和金属Ga物种,这二者随着温度的继续升高逐渐向体相扩散。在Pd（111）表面预吸附O和H对上述吸附和解离行为存在显著的影响。当表面预吸附H时,脱附产物CH₄和H₂的脱附主要位于315 K,可归属为一甲基镓的解离脱附。当表面预吸附O时,只在258 K观察到CH₄和H₂的脱附峰,可能来自于Pd-O-Ga（CH₃）₂吸附结构的解离.     

The HO4H → O3 + H2O reaction catalysed by acidic,neutral and basic catalysts in the troposphere

A detailed effects of catalyst X (X?=?H₂O, (H₂O)₂, NH₃, NH₃···H₂O, H₂O···NH₃, HCOOH and H₂SO₄) on the HO₄H → O₃?+?H₂O reaction have been investigated by using quantum chemical calculations and canonical vibrational transition state theory with small curvature tunnelling. The calculated results show that (H₂O)₂-catalysed reactions much faster than H₂O-catalysed one because of the former bimolecular rate constant larger by 2.6–25.9 times than that of the latter one. In addition, the basic H₂O···NH₃ catalyst was found to be a better than the neutral catalyst of (H₂O)₂. However it is marginally less efficient than the acidic catalysts of HCOOH, and H₂SO₄. The effective rate constant (k'_t) in the presence of catalyst X have been assessed. It was found from k'_t that H₂O (at 100% RH) completely dominates over all other catalysts within the temperature range of 280–320?K at 0?km altitude. However, compared with the rate constant of HO₄H → H₂O?+?O₃ reaction, the k _eff values for H₂O catalysed reaction are smaller by 1–2 orders of magnitude, indicating that the catalytic effect of H₂O makes a negligible contribution to the gas phase reaction of HO₄H → O₃?+?H₂O.

Highlights

• A detailed effects of catalyst of H₂O, (H₂O)₂, NH₃, NH₃···H₂O, H₂O···NH₃, HCOOH and H₂SO₄ on the HO₄H → O₃?+?H₂O reaction has been performed.

• From energetic viewpoint, H₂SO₄ exerts the strongest catalytic role in HO₄H → O₃?+?H₂O reaction as compared with the other catalysts.

• At 0 km altitude H₂O (at 100% RH) completely dominates over all other catalysts within the temperature range of 280–320 K.

• HO₄H → H₂O?+?O₃ reaction with H₂O cannot be compete with the reaction without catalyst, due to the fact that the effective rate constants in the presence of H₂O are smaller.

     

Luminescence characteristics of Na21(SO4)7F6Cl:Cu+ phosphor

Copper-doped Na₂₁(SO₄)₇F₆Cl phosphor was synthesized via the conventional wet chemical method. The synthesis was carried using CuCl₂ and Cu (NO₃)₂·3H₂O as dopants in two different steps successively. The formation and phase purity of the compound were revealed by the X-ray diffraction pattern. Functional groups of the prepared phosphor were observed in the FT–IR spectrum. The emission along with excitation spectra were followed to explore the luminescence attributes. Photoluminescence (PL) emission spectrum of the material synthesized using CuCl₂ as the dopant was observed at 358?nm due to 3d^l0?3d⁹4s transitions when excited around 247?nm for various copper concentrations. Efficient blue emissions were obtained at peaks 423 and 469?nm for materials synthesized using Cu (NO₃)₂·3H₂O as the dopant, when monitored at 357?nm excitation. The Commission Internationale de I’Eclairage chromaticity coordinates for different copper concentrations were calculated for the emission around 423?nm. TL glow curves of Na₂₁(SO₄)₇F₆Cl:Cu phosphor for different dopant concentrations, irradiated with 100?Gy gamma dose, were studied and hence the trap parameters, namely order of kinetics (b), activation energy (E) and frequency factor (s) associated with the most intensive glow peak of Na₂₁(SO₄)₇F₆Cl:Cu phosphor were determined by using Chen’s Peak shape method. The results indicate that Na₂₁(SO₄)₇F₆Cl:Cu⁺ is a potential novel blue-emitting lamp phosphor and may be quite suitable for use in dosimetry of ionizing radiations.     

Infrared absorption of iodomethylperoxy (syn-ICH2OO) radical generated upon photolysis of CH2I2 and O2 in solid para-H2

Irradiation of a para-hydrogen (p-H₂) matrix containing diiodomethane (CH₂I₂) and O₂ at 3.2 K with light at 280 ± 20 nm, followed by annealing of the matrix at 4.0 K, yielded infrared (IR) absorption lines at 2982.4, 1408.9, 1231.8, 1226.5/1225.6, 1085.6, 917.7, 841.6/841.1, 550.5, and 490.2 cm^?1 that are assigned to the syn-iodomethylperoxy (syn-ICH₂OO) radical. Further irradiation of the matrix at 365 nm diminished these features. Experiments with CH₂I₂ and ¹⁸O₂ yielded lines of syn-ICH₂¹⁸O¹⁸O at 1407.3, 1228.1/1227.7, 1217.7/1217.0, 1031.5, 899.9/899.4, 836.7/836.0, and 473.6 cm^?1. The assignments are based on the photolytic behaviour and comparisons of observed vibrational wavenumbers, IR intensities, and ¹⁸O-isotopic shifts with those predicted with the B3LYP/aug-cc-pVTZ-pp method. The observation is consistent with a mechanism that, upon photolysis of CH₂I₂ at 280 nm, CH₂I was formed and subsequently reacted with O₂ to yield syn-ICH₂OO. Compared with the gaseous reaction CH₂I + O₂ → CH₂OO + I at low pressure, observation of ICH₂OO in a p-H₂ matrix instead of CH₂OO in the gaseous phase indicates that the excess energy of internally excited ICH₂OO, produced upon reaction of CH₂I + O₂, was rapidly quenched in the matrix so that ICH₂OO became readily stabilised without further decomposition to form CH₂OO + I.     

Electron paramagnetic resonance of Mn2+ and Gd3+ in Pr2Zn3(NO3)12.24 H2O single crystals

The electron paramagnetic resonance of Mn²⁺ and Gd³⁺ doped in Pr₂Zn₃(NO₃)₁₂.24H₂O single crystals has been studied at X-band. Mn²⁺ substitutes for two Zn²⁺ sites, while Gd³⁺ substitutes for single type of Pr³⁺ sites. The spin-Hamiltonian analysis of the EPR spectra is presented at 298 K as well as 77 K.     

Can (H2O) n (n = 1–2) as effective catalysts in the CH2OO + H2S reaction under tropospheric conditions?

The addition reaction of CH₂OO?+?H₂S → HSCH₂OOH without and with catalyst X (X?=?H₂O and (H₂O)₂) has been investigated by CCSD(T)-F12a/VTZ-F12//B3LYP/aug-cc-pVTZ method and canonical variational transition state theory with small curvature tunneling correction. When H₂O was introduced in the CH₂OO?+?H₂S reaction, it not only acts as a catalyst for producing HSCH₂OOH, but also plays as a reactant to forming HOCH₂OOH. The formation channel of HSCH₂OOH is more important than the formation channel of HOCH₂OOH with its calculated rate constant larger by 11.0–43.2 times within the temperature 280–320?K. Then, (H₂O)₂ catalysed CH₂OO?+?H₂S → HSCH₂OOH reaction has been taken into account with its rate lower 1.9–4.2 times than the reaction of CH₂OO?+?H₂S → HSCH₂OOH with water. Also, CH₂OO?+?H₂S with H₂O cannot compete with the CH₂OO?+?H₂S reaction without water. This is different from CH₂OO?+?(H₂O)₂ reaction, which is about 4 orders of magnitude larger than the rate constant for CH₂OO?+?H₂O reaction. Such discrepancy is possible because C(CH₂OO)···O(H₂O) interaction has been enhanced more obviously by H₂O as compared to that of C(CH₂OO)···O(H₂S) interaction.     

The infrared and laser Raman spectra of K2Zn(SO4)2 · 6H2O

The Raman spectra of the single crystal of K₂Zn(SO₄)₂·6H₂O belonging toC _2h ⁵ space group in the 40–1200 cm⁻¹ region in different scattering geometries and their spectra ofthe microcrystalline salt in the 1500-50 cm⁻¹ region have been reported. The dynamics of the crystal has been described in terms of 186 phonon modes under the unit cell approximation. The weak bands in the region 400–900 cm⁻¹ have been assigned to the libratory modes of H₂O molecules in contradiction to the assignments reported by Ananthanarayanan. The ambiguities existing in the literature about the assignments ofν ₂ ^c andν ₅ ^c modes of [Zn(H₂O)₆]²⁺ have also been removed. The translatory and libratory modes of different units of the crystal have been identified and assignments are made using farir and Raman data on various isomorphous tutton salts. It has been inferred that both SO ₄ ²⁻ tetrahedron and [Zn(H₂O)₆]²⁺ octahedron undergo linear as well as angular distortions from their free state symmetries in the crystal.     

New FIR laser lines from optically pumped C2H3F, C2H3Cl, C2H3Br, C2H3CN, C2H5F, CH2CF2, HCOOH and CH3Br

Twenty-seven new cw far infrared laser lines with wavelengths between 137 and 988m have been observed from optically pumping C₂H₃F, C₂H₃Cl, C₂H₃Br, C₂H₅F, C₂H₃CN, CH₂CF₂, HCOOH and CH₃Br with a CO₂ laser. The wavelengths of these FIR laser lines were determined together with their optimum pressures and relative intensities.     

DSC study of superionic phase transition in (NH4)4H2(SeO4)3 single crystals

DSC and complex impedance studies of the protonic conductor (NH₄)₄H₂(SeO₄)₃, which undergoes a superionic phase transition of first order at T_s = 378 K show that the activation energy of ionic conductivity d(lg σ)/dt and the ordering enthalpy ΔC_p of the crystal are proportional: d(lg σ)/dT = XΔC_p/RT_s + const, as found for MAg₄I₅ crystals undergoing a second-order superionic phase transition. Thus the short-range order environment of the species involved in fast-ion transport plays the main role in the superionic phase transition. This is also supported by the value of the entropy change at T_s, ΔS = 43 J/mole·K. A new metastable phase was found to be induced on heating the (NH₄)₄H₂(SeO₄)₃ crystal above T_s.     

(H2O)6的稳定结构及异构过程研究

(H₂O)₆是形成三维立体结构的最小水分子团簇并具有能量较低的多个稳定异构体.本文利用从头计算方法研究了各稳定结构的异构化过程.(H₂O)₆的环状结构与最稳定结构的能量差0.31 eV为一个氢键的键能.水分子团簇的异构化是分子间氢键打开或重组的过程,不同异构体之间的转化每次只涉及一个氢键的打开或重组,异构化的能垒高度在0.07—0.21 eV之间. 关键词： 水分子团簇 2O)₆')" href="#">(H₂O)₆ 异构化过程 从头计算     

氢同位素氚水T2O(X1A1)的解析势能函数

获得T₂O(X¹A₁)解析势能函数的主要困难在于Born-Oppenheimer近似下T₂O(X¹A₁)与H₂O(X¹A₁)势能函数的不可区分性.然而,在Born-Oppenheimer近似下,分子势能函数实际上是键长、键角这些 关键词： 2O(X¹A₁)')" href="#">T₂O(X¹A₁) 同位素效应 解析势能函数     

The thermoelastic properties of [N(CH3)4]2ZnBr4 and [N(CH3)4]2MnBr4

The ferrodistortive phase transition in the bis-tetramethylammonium tetrabromide crystals below room temperature is studied within the framework of the Landau theory. The specific heats of [N(CH₃)₄]₂MnBr₄ and [N(CH₃)₄]₂ZnBr₄ are correctly described down to 40°C below the transition temperature. The phenomenological parameters are determined from calorimetric results, elastic constants and thermal expansion data. Using these coefficients, the monoclinic angle in the ferrodistortive phases is obtained. The anharmonic quantities, such as the isothermal compressibility, calculated from the specific heat data, are in good agreement with the values derived from the elastic measurements.     

Additivity and non-additivity of dissociation energies in intermolecular interactions. Theoretical studies on (H2)n,n = 2-8, (CO2)n,n = 2-6 and (HF)n,n = 2-8

CCSD(T) and MP2 results using the aug-cc-pV5Z basis set are reported for chain, cyclic and other structures of the clusters (H₂)_n, n?=?2-8, (CO₂)_n, n?=?2-6 and (HF)_n, n?=?2-8. In chain-like structures of (H₂)_n and (CO₂)_n, with the bonding type of the dimer maintained, the dissociation energy D_e of the dimer doubles for the trimer, triples for the tetramer, and so on. Due to these systems being dominated by short-range forces, interactions are essentially restricted to neighbouring monomers. For other types of (H₂)_n and (CO₂)_n structures, the multipliers relative to the dimerisation energy can be much higher. Dissociation energies for the hexamers in S₆ symmetry of both H₂ (379?cm^?1) and CO₂ (4925?cm^?1) are over ten times the respective dimerisation energies. For the chain-like trimer of HF, however, D_e is in excess of double the dimer value. Mainly due to longer-range dipolar forces, the interactions reach beyond the neighbouring monomers. The interaction energy between HF monomers in chains follows an approximate R^?2 (R being the F–F distance) relationship, The calculated dissociation energies of the HF octamer are 15,985?cm^?1 (factor of 10.4) for the chain, and 21,003?cm^?1 (factor of 13.7) for the C_6h cyclic structure.     

FC(O)O2的结构及其自由基与NO反应的微观机理研究

用密度泛函理论(DFT)和哈特里-福克(HF)从头计算方法和半经验势方法等研究了FC(O)O₂ 的结构和振动性质.在DFT中采用B3LYP方法,在6-311G(d)基组上对FC(O)O₂自由基与NO反应的微观过程进行了分析.首先给出了各反应物、中间体、过渡态和生成物的几何构型,然后计算了它们的能量和频率,通过频谱分析得到反应的中间体和过渡态信息,即FC(O)O₂与NO反应为多反应通道,势垒高度和反应速度给出主要通道是FC(O)O₂     

Conductivity and water uptake of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O

The hydrated oxygen deficient complex perovskite-related materials Sr₄(Sr₂Nb₂)O₁₁·nH₂O and Sr₄(Sr₂Ta₂)O₁₁·nH₂O were studied at high water vapour pressures over a large temperature range by electrical conductivity measurements, thermogravimetry (TG), and X-ray powder diffraction (XRPD). In humid atmospheres both materials are known to exhibit protonic conductivity below dehydration temperatures, with peak-shaped maxima at about 500 °C. In this work we show that the peaks expand to plateaus of high conductivity from 500 to 700 °C at a water vapour pressure of 1 atm. However, in situ synchrotron XRPD of Sr₄(Sr₂Nb₂)O₁₁·nH₂O as a function of temperature shows that these observations are in fact coincident with melting and dehydration of a secondary phase Sr(OH)₂. The stability of Sr₄(Sr₂Nb₂)O₁₁·nH₂O and Sr₄(Sr₂Ta₂)O₁₁·nH₂O in humid atmospheres is thus insufficient, causing decomposition into perovskites with lower Sr content and SrO/Sr(OH)₂ secondary phases. This, in turn, rationalizes the observation of peaks and plateaus in the conductivity of these materials.     

Crystal structure of di-(L-serine) phosphate monohydrate [C3O3NH7]2H3PO4H2O

The crystal structure of di-(L-serine) phosphate monohydrate [C₃O₃NH₇]₂H₃PO₄H₂O is determined by single-crystal x-ray diffraction. The intensities of x-ray reflections are measured at temperatures of 295 and 203 K. The crystal structure is refined using two sets of intensities. It is established that, in the structure, symmetrically nonequivalent molecules of L-serine occur in two forms, namely, the monoprotonated positively charged molecule CH₂(OH)CH(NH₃)⁺COOH and the zwitterion CH₂(OH)CH(NH₃)⁺COO^?, which are linked with each other and with the H₂PO ^?₄ ion through a hydrogen-bond system involving water molecules.