Ag adsorption on Cd-terminated CdS (0 0 0 1) and S-terminated CdS (0 0 0 1?) surfaces: First-principles investigations

First-principles calculations are performed to study the adsorption of Ag at Cd-terminated CdS (0 0 0 1) and S-terminated CdS (0 0 0 1?) surfaces as a function of Ag coverage. Our results reveal that Ag adsorption at Cd-terminated (0 0 0 1) has a large binging energy than at S-terminated (0 0 0 1?) surface. For Ag adsorption at Cd-terminated (0 0 0 1) surface, T4 structure is more favorable and the Ag-Cd bond posses an ionic-like character. While for Ag adsorption at S-terminated (0 0 0 1?) surface, the H3 structure is most stable and the bonding between Ag-S is covalent. It is found that the magnitude and the sign of surface dipole moment are partly determined by the difference between the electronegativities of Ag and the host atom bonding with Ag. The adsorption energy changes as a function of Ag coverage. In addition, related properties of Ag cluster adsorption at Cd-terminated (0 0 0 1) surface are also discussed.     

Collision energy effect on the H′ + BrH (ν = 0, j = 0) → H′Br + H reaction: A quasi-classical trajectory study

Theoretical studies on the dynamics of the exchange reaction H′ + BrH (ν = 0, j = 0) → H′Br + H are performed on potential energy surface (PES) (Kurosaki et al., private communication) for the ground state using the quasi-classical trajectory method. The cross sections, computed at the collision energies (E_c) of 0.5-2.0 eV, are in good agreement with the earlier quantum wave packet results. The rotational, vibrational, and translational fractions in the total energy and the vibrational distribution for the product molecule are calculated at the same collision-energy range. The results support the repulsive character of the PES. In the considered E_c range, it has little chance to occur in an indirect reaction. The alignment and orientation of the product H′Br are investigated in detail with stereodynamics. The results show that E_c can effect on both the alignment and the orientation of product.     

Liquid–liquid equilibria for water + 1-propanol/2-propanol + potassium chloride + cesium chloride quaternary systems at 298.1 ± 0.1 K

In this paper, we present the results of our study of the phase equilibria for two quaternary systems: water + 1-propanol/2-propanol + potassium chloride (KCl) + cesium chloride (CsCl) at 298.1 ± 0.1 K. We also produced the binodal curves and tie-lines at different KCl/CsCl mass-fraction ratios, and produced integrated phase diagrams for the quaternary systems. We also discuss the solvation abilities of KCl and CsCl, and the effect of the polarity of the organic solvent on the liquid–liquid equilibrium. We compared the experimental tie-lines derived for the quaternary systems with values predicated by modifying the Eisen–Joffe equation. The model produced satisfactory results.     

Vapor–liquid equilibria and density measurement for binary mixtures of o-xylene + NMF, m-xylene + NMF and p-xylene + NMF at 333.15 K, 343.15 K and 353.15 K from 0 kPa to 101.3 kPa

Isothermal vapor–liquid equilibria at 333.15 K, 343.15 K and 353.15 K for three binary mixtures of o-xylene, m-xylene and p-xylene individually mixed with N-methylformamide (NMF), have been obtained at pressures ranged from 0 kPa to 101.3 kPa over the whole composition range. The Wilson, NRTL and UNIQUAC activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Peng–Robinson equation of state in calculating the vapor mole fraction. Liquid and vapor densities were measured by using two vibrating tube densitometers. The excess molar volumes of the liquid phase were also determined. Three systems of o-xylene + NMF, m-xylene + NMF and p-xylene + NMF mixtures present large positive deviations from the ideal solution and belong to endothermic mixings because their excess Gibbs energies are positive. Temperature dependent intermolecular parameters in the NRTL model correlation were finally obtained in this study.     

La0．67Ca0．33Mn1-xCrxO3（0．0≤x≤0．15）中的异常CMR效应

研究了Mn位掺Cr体系La0．67Ca0．33Mn1-xCrxO3(0．0≤x≤0．15)的磁性和磁电阻性质，发现Cr掺杂对居里温度Tc影响不明显，但是导致了反常的电输运和磁电阻行为，随着Cr含量的增加，起始电阻率峰向低温移动，同时电阻率出现一个附加峰。在磁场作用下，两个电阻率峰被强烈压缩，导致CMR效应中出现双峰，并且CMR效应的温区被极大地拓宽了，从低温直到接近室温。这个结果表明：Mn位元素替代是调节CMR效应的有效方法。     

0Author Index

A. PANAYE 14 Cheng Chieh-Yuan 16 AI Chang-chun 139 Cheng Jin-Pei 100 Albert S. C. Chan 2 Cheng Tie-ming 28 André Giroux 13 Chi Kai-Ming 122 B Chien Shu-Hua 121 Badry Bursulaya …     

《色谱》第 2 0卷 (2 0 0 2年 )总目次

研究报告胰蛋白酶水解全酪蛋白反应过程中的色谱分析齐　崴 ,何明霞 ,何志敏 ,史德青 (1)……………………………………………多氯代二苯并呋喃的结构信息连接性指数与其在不同色谱柱上的气相色谱保留行为的关系余训民 ,杭义萍 (6 )……………苯乙烯 氧乙烯 苯乙烯三嵌段聚合物的受限结晶行为的反气相色谱分析陈胜洲 ,邹其超 ,张金枝 (12 )…………………………遗传算法用于液相色谱分离条件的优化陈学国 ,倪坚毅 ,邹汉法 ,赵瑞环 (97)……………………………………………………种子溶胀悬浮聚合法制备分子印迹聚合物微球成国祥 ,张立永 ,付…     

High-efficiency hydrophilic interaction chromatography by coupling 25 cm × 4.6 mm ID × 5 μm silica columns and operation at 80 °C

Recently, hydrophilic interaction chromatography (HILIC) has emerged as a valuable orthogonal tool to reversed-phase liquid chromatography (RP-LC) as it allows for resolution of highly polar ionisable compounds. The relationships between separation efficiency, column length and speed of analysis for 4.6 mm ID × 5 μm silica particle columns in HILIC are demonstrated using kinetic plots. The kinetic plots constructed for conventional pressure systems operating at 350 bar and at 30 °C and 80 °C are confirmed using experimental data for different column lengths. Efficiencies of more than 130,000 theoretical plates could be achieved by connecting up to six columns of 25 cm. As expected, a significant gain in analysis speed without loss of efficiency could be obtained by operating at 80 °C compared to 30 °C. The advantages of using long columns in HILIC in combination with elevated column temperature for the pharmaceutical industry are illustrated using test mixtures comprised of commercially available ionisable compounds (including some containing functional groups with potential genotoxic typical structural alerts) as well as real polar ionisable pharmaceuticals.     

Theoretical insight into stereodynamics of the O(D) + H2 (v = 0–3, j = 0) → OH + H reaction: A quasiclassical trajectory (QCT) study

In this work, the reaction O(¹D) + H₂ → OH + H has been theoretically studied using the quasiclassical trajectory (QCT) method developed by Han and co-workers. All the quasiclassical trajectory calculations are performed on the DK (Dobbyn and Knowles) potential energy surface (PES). The vector correlation information on the reaction O(¹D) + H₂ → OH + H has been obtained. It has been demonstrated that the product alignment is sensitive to the reactant vibrational quantum number (v) at collision energy of 19 kcal/mol. Moreover, with increasing the value of v, backward scattering becomes weaker and forward scattering becomes stronger.     

《化学进展》2 0 0 3年度分类索引

无机化学锂无机固体电解质 15 ( 2 ) ,10 1多元多金属含氧簇合物在催化化学中的应用 15 ( 2 ) ,15 1新型无机聚合物的设计合成、结构规律与性能研究 15 ( 4 ) ,2 49无机晶须材料的合成与应用 15 ( 4 ) ,2 64氨基酸配合物的性质及应用 15 ( 4 ) ,2 88化学气相沉积法制备氮化钛 15 ( 5 ) ,3 74Ti O2 形态结构与光催化活性关系的研究 15 ( 5 ) ,3 79中孔氧化硅的超分子模板合成及其结构与形貌的调控 15 ( 6) ,477有机化学Ugi反应的研究新进展 15 ( 3 ) ,186用组合化学建立天然产物类似物库 15 ( 3 ) ,194用不保护或少保护的糖基受体合成寡糖 …     

Liquid–liquid equilibrium of the ternary system water + acetic acid + sec-butyl acetate

Experimental liquid–liquid equilibrium (LLE) of the water–acetic acid–sec-butyl acetate ternary system was investigated at 298.15, 303.15, 308.15 and 313.15 K and at atmospheric pressure. Separation factors were also evaluated for the immiscibility region. The NRTL and UNIQUAC models were applied to fit the experimental data for the ternary system. The binary interaction parameters obtained from both models were found to be successfully correlated with the equilibrium compositions. The UNIFAC group contribution method was employed to predict the observed ternary LLE data. It was found that four types of the UNIFAC model (UNIFAC, UNIFAC-LL, UNIFAC-DMD, and UNIFAC-LBY) did not provide a good prediction of the LLE data for this ternary system.     

La0．8Sr0．2Mn1-xCoxO3（x=0，0．3，0．5，1）的磁性转变

采用柠檬酸络合法制备B位掺杂的纳米钙钛矿复合氧化物La0．8Sr0．2Mn1-xCoxO3（x=0，0．3，0．5，1．0）。应用X射线衍射法（XRD）进行结构的测定与分析，并结合扫描电镜（SEM）和热磁曲线（M-T曲线）的实验结果，研究这4种样品的结构和磁性之间的关系。X射线衍射实验分析表明4个样品均属六方晶系，M-T曲线得出的1／χ-T曲线表明：La0．8Sr0．2MnO3是铁磁性，La0.8Sr0．2Mn0．7Co0．3O3和La0．8Sr0．2Mn0.5Co0．5O3是亚铁磁性，而La0．8Sr0．2CoO3是反铁磁性的。利用电镜观察到前3种样品均为颗粒状，颗粒之间首尾相接形成链状结构，并进一步由链状结构支起一个个的空间网状结构，最后一种样品为较为分散的颗粒。     

Vapor–liquid equilibrium for the binary systems tetrahydrothiophene + toluene and tetrahydrothiophene + o-xylene at 368.15 K and 383.15 K

Isothermal vapor–liquid equilibrium (VLE) for tetrahydrothiophene + toluene and tetrahydrothiophene + o-xylene at 368.15 K and 383.15 K was measured with a recirculation still. Liquid- and vapor-phase compositions were determined with gas chromatography. All systems exhibit a small positive deviation from Raoult's law and show nearly ideal behavior. All VLE measurements passed the point test used. The experimental results were correlated with the Wilson model and compared with COSMO-SAC predictive models. COSMO-SAC predictions show a slight negative deviation from Raoult's law for all systems measured. Raoult's law can be used to describe all systems studied. The activity coefficients at infinite dilution are presented.     

Isobaric vapor–liquid equilibria for water + n-propanol + n-butanol ternary system at atmospheric pressure

Isobaric vapor–liquid equilibrium (VLE) data for water + n-propanol + n-butanol ternary system have been extensively measured at 99.2 kPa using a recirculating still. The experimental data were then correlated using the extended UNIQUAC model, in which the binary interaction energy parameters between the three components were obtained through a simplex fitting method. The results showed that the calculated data by the extended UNIQUAC model using the same interaction energy parameters agree well with both the experimental data and the literature data. It demonstrated that the experimental data are very consistent with the literature data; and the extended UNIQUAC model is reliable to predict the VLE of the ternary system using the obtained interaction energy parameters.     

Vapor–liquid equilibrium measurement and modeling for the difluoromethane + pentafluoroethane + propane ternary mixture

Vapor–liquid equilibrium data for the difluoromethane (R32) + pentafluoroethane (R125) + propane (R290) ternary mixture were measured at 5 isotherms between 263.15 K and 323.15 K. The measurement was carried out using a circulation-type apparatus recently developed, which was validated with binary mixtures. With binary interaction parameters obtained for the three corresponding binary mixtures, VLE modeling and prediction were performed for the ternary mixture using the Peng–Robinson equation of state with the classical mixing rules and MHV1 mixing rules. Hou's group contribution model for VLE of new refrigerant mixtures was further tested with the experimental data for the ternary system. The predicted pressure and vapor phase composition were compared with experimental ones.     

Liquid–liquid equilibrium of (water + 1-propanol + 1-pentanol) system at 298.15 and 323.15 K

Liquid–liquid equilibrium data for the ternary system water + 1-propanol + 1-pentanol have been determined experimentally at 298.15 and 323.15 K using “static–analytic” apparatus involving ROLSI™ samplers. The experimental data are correlated considering both NRTL and UNIQUAC activity coefficient models. The results obtained show the ability of both models for the determination of liquid–liquid equilibrium data of the studied system. The reliability of the experimental tie-line data is determined through the Othmer–Tobias and Bachman equations.     

La0．67Ca0．33MnO3／La0．67Sr0．33CoO3／La0．67Ca0．33MnO3三层薄膜中的磁性耦合

研究了对靶溅射技术制备的La0．67Ca0．33MnO3／La0．67Sr0．33CoO3／La0．67Ca0．33MnO3三层薄膜中的磁输运特性。由于La0．67Sr0．33CoO3层的电阻短路效应，三层膜的磁阻随中间层厚度的增加而迅速减小。与La0．67Ca0．33MnO3单层膜不同，三层膜显示出增强的金属-绝缘体转变温度(TMS)。在230K时，系统的矫顽力Hc随中间层厚度非单调地变化，磁滞回线的形状表明了两层La0．67Ca0．33MnO3之间存在着磁性耦合。     

C~6~0, C~7~0的烷基化

本文利用低价稀土化物(S~mI~2或YbI~2)与C~6~0、C~7~0及卤代烃(烯丙基溴、氯苄)的混合溶液反应,制得烯丙基化、苄基化的富勒烯。发现与C~6~0相接的苄基数可以从1到14,验证了Krusic等人的结果。此外,还发现C~6~0可以进行烯丙基化,得到(CH~2=CHCH~2)~nC~6~0(n=1-10),C~7~0可以进行苄基化,C~7~0上至少可以接13个苄基,实验证明这类反应是对富勒烯进行烷基化的一种简便、有效的方法。     

Liquid–liquid equilibrium of ternary systems 1-octyl-3-methylimidazolium hexafluorophosphate + aromatic + aliphatic hydrocarbons

The phase behavior of six ternary systems involving an aromatic hydrocarbon (benzene, toluene or m-xylene), an aliphatic hydrocarbon (nonane or undecane), and an ionic liquid (1-octyl-3-methylimidazolium hexafluorophosphate, [omim][PF₆]) was experimentally studied at 298.15 K and atmospheric pressure, totalizing 26 tie-lines. The main goal is to determine if [omim][PF₆] is a good solvent for the separation of the aromatic and aliphatic compounds, a common operation in the processing of reformed naphtha. All the ternary diagrams are of type 1, with high and wide two-phase regions, which show that [omim][PF₆] is a good solvent for the extraction of aromatic from aliphatic hydrocarbons. The Othmer–Tobias correlation was used for evaluation of the quality of the tie-line data, with good results. The data were correlated with the NRTL model for the activity coefficient, with estimation of new interaction energy parameters by using a modified Simplex method and a composition-based objective function. The results, expressed by root mean square deviations between experimental and calculated compositions, are very satisfactory.