定标粒子理论预测乙醇—水体系汽液平衡盐效应

测定了７０℃下３个１－１型电解质在各种不同浓度的乙醇－水体系中的汽液平衡盐效应参数，并给出用定标粒子理论计算盐效应参数的方法，硬球作用项采用Ｍａｓｔｅｒｔｏｎ－Ｌｅｅ方程，软球作用项采用胡英的径向分布函数。分子间力在Ｌｅｎｎａｒｄ－Ｊｏｎｅｓ位能函数基础上计入偶极－偶极、偶极－诱导偶极、电荷－偶极、电荷－诱导偶极的贡献，其中离子－分子间的静电作用项仅限于规则排列的第一配位圈之内、将混合溶剂的局部介     

极性—非极性双液体系汽液平衡盐效应参数的测定与计算

测定了苯—甲醇— 1_1型电解质 (LiCl、NaBr、KI)、四氯化碳—甲醇— 1_1型电解质 (LiCl、NaBr、KI)两个体系在恒压 ( 1 0 1 .3kPa)条件下的汽液平衡盐效应参数。理论计算以Pierotti的定标粒子理论为基础 ,硬球作用项采用Masterton -Lee方程计算 ,软球作用项采用胡英等人建议的简化的径向分布函数 ,分子间力在Lennard -Jones位能函数基础上计入极性分子间偶极—偶极、偶极—诱导偶极 ,离子与极性分子间的电荷—偶极以及离子与分子间的电荷—诱导偶极的贡献 ,并根据溶剂性质和溶液结构作出一些合理的假设。在此基础上 ,理论计算与实验结果基本相符。     

定标粒子理论计算非水溶液的盐效应常数

本文应用定标粒子理论计算了非电解质溶质在盐(NaI、或KI)和环丁砜组成的非水电解质溶液中溶解度的盐效应常数。硬球作用项采用Masterton-Lee的方法。软球作用项采用胡英等的径向分布函数处理方法, 并考虑进了偶极-偶极、偶极-诱导偶极、电荷-偶极和电荷-诱导偶极等相互作用。分子的硬球直径σ和能量参数∈/k由经验方程计算。由理论值和实验结果比较得出: 当σ_2取0.563 nm、离子半径取电子密度标度时, 理论值与实验值符合得较好。     

YbCl_3－CaCl_2－NaCl三元体系相图的研究

借助ＤＴＡ研究了ＹｂＣｌ３－ＣａＣｌ２－ＮａＣｌ三元体系相图，发现该体系有对应于ＹｂＣｌ３、ＣａＣｌ２、ＮａＣｌ、Ｎａ３ＹｂＣｌ６的４个液相面，５条二次结晶线，１个三元低共熔点Ｅ（８７．０％ＹｂＣｌ３，１．０％ＣａＣｌ２，１２．０％ＮａＣｌ；４５０℃）和三元转熔点Ｐ（６１．０％ＹｂＣｌ３，１９．０％ＣａＣｌ２，２０．０％ＮａＣ１；４７４℃）。     

YbCl3—CaCl2—NaCl三元体系相图的研究

借助ＤＴＡ研究了ＹｂＣｌ３－ＣａＣｌ２－ＮａＣｌ三元体系相图，发现该体系有对应于ＹｂＣｌ３、ＣａＣｌ２，Ｎａ３ＹｂＣｌ６的４个液相面，５条二次结晶线，１个三元低共熔点Ｅ（８７．０％ＹｂＣｌ３，１．０％ＣａＣＬ２，１２．０％ＮａＣＬ；４５０℃）和三元转熔点Ｐ（６１．０％ＹｂＣｌ３，１９．０％ＣａＣｌ２，２０．０％ＮａＣｌ；４７４℃）。     

钕在含NdCl3体系中溶解损失的研究

测定了金属钕在ＮｄＣｌ３－ＭＣｌｎ体系、ＮｄＣｌ３－（９０．０ｗｔ％ＫＣｌｎ）（Ｍ＝Ｌｉ，Ｎａ，Ｋ，Ｃａ，Ｓｒ，Ｂａ；ｎ＝１或２）截面和ＮｄＣｌ３－ＬｉＦ体系（富ＮｄＣｌ３区）中的溶解损失。发现钕在ＮｄＣｌ３－ＫＣｌ，ＮｄＣｌ３－ＣａＣｌ２和ＮｄＣｌ３－（９０．０ｗｔ％ＫＣｌ，１０．０ｗｔ％ＣａＣｌ２）体系中溶解损失较小，而在ＮｄＣｌ３－ＫＣｌ体系中随温度的升高而加大，当体系中ＮｄＣｌ３浓度＜５０     

环糊精诱导室温Ling光法中两种新型简便快速的防氧方法

在环糊精诱导室温Ｌｉｎｇ光法中除氧技术是重要的实验条件。本文首次成功地建立了在反应体系中以Ｚｎ（ｓ）＋ＨＣｌ产生Ｈ２和Ｎａ２ＣＯ３＋ＨＣｌ产生ＣＯ２作除氧剂，α－氯代萘作模型化合物的ＣＤ－ＲＴＰ法。     

Nd（ClO_4）_3和Er（ClO_4）_3与α－双（苯基亚砜）甲烷配合物的

研究了Ｎｄ（ＣｌＯ４）３·ｎＨ２Ｏ－ｂｐｈｓｍ［双（苯基亚砜）甲烷１体系（甲醇－氯仿１：２）和Ｅｒ（ＣｌＯ４）３·ｎＨ２Ｏ－ｂｐｈｓｍ体系（甲醇－氯仿１：２）的电子光谱。分析了在可见光区内，ｆ一ｆ跃迁的强度和强度参数，并从Ｎｄ３＋和Ｅｒ３＋的超灵敏跃迁的振子强度和强度参数Ｔ２与配体ｂｐｈｓｍ浓度的关系，指出了体系中Ｎｄ与ｂｐｈｓｍ形成１：２．５的物种和Ｅｒ３＋与ｂｐｈｓｍ形成１：２的物种。     

超球谐展开的收敛行为He原子的^3S态

利用相关函数－超球谐－广义Ｌａｇｕｅｒｒｅ函数方法，研究Ｈｅ原子＾３Ｓ态波函数向超球谐函数展开的收敛行为。截止于ｌ＝０，１，２的超球谐函数给出的本征能分别与组态相互作用的ｓ－，ｓｐ－，ｓｐｄ－极限能一致。仅用４４个超球谐函数，便得到了与精确的ＨｙｌｌｅｒａａｓＣＩ变分能量小数点后第５位的２＾３Ｓ，３＾３Ｓ的４＾３Ｓ态本征能吻合。     

流动注射—氢化物发生—非色散原子荧光光谱法直接测定海水中的砷（Ⅲ）和砷（

用流动注射－氢化物发生－非色散原子荧光光谱法对海水中Ａｓ（Ⅲ）和Ａｓ（Ⅴ）的直接测定进行了研究,氢化物发生的最佳条件为：ＫＨＢ４溶液浓度为５ｇ．Ｌ＾－１（含ＫＯＨ５ｇ．Ｌ＾－１）,流速１０．０ｍＬ．ｍｉｎ＾－１;样品酸度为１．３ｍｏｌ．Ｌ＾－１ＨＣｌ,流速４．２ｍＬ．ｍｉｎ＾－１。对基体ＮａＣｌ,ＭｇＣｌ２,ＣａＣｌ２,Ｎａ２ＳＯ４以及微量共存金属离子（Ｃｄ,Ｚｎ,Ｐｄ,Ｃｕ）的干扰实验结果表明,基体和微量共存金属离子对Ａｓ（Ⅲ）的测定没有干扰。样品中Ａｓ（Ⅴ）的测定用硫脲进行预还原,通过总量和Ａｓ（Ⅲ）的含量的差减得到Ａｓ（Ⅴ）含量,在优化实验条件下下测量方法的检出限（３σ）为０．０８ｎｇ．ｍＬ＾－１;７次测定的相对标准偏差为０．４８％－１．３０％（８．０ｎｇ．ｍＬ＾－１标准溶液）。标准曲线和标准加入法对海水     

Molecular thermodynamics of salt effect in vapor–liquid equilibrium of ethanol–water systems

Scaled particle theory was used to derive a general expression for the salt effect parameter, K, of isobaric vapor–liquid equilibrium for ethanol–water-1-1 type electrolytic systems, which appears in the Furter equation. This expression was essentially a sum of two terms: 1, the hard sphere interaction term calculated by Masterton–Lee's equation, 2, the soft sphere interaction term calculated by Y. Hu's molecular thermodynamical model, in which the diameters of nacked ions were replaced by that of solvated ions, the solvation coefficients (i.e., in the radio of the latter to the former) were taken to be adjustable parameters, their magnitude implies the ionic solvation rules. A correlation equation for the local dielectrical constant around central ions with liquid concentration was obtained by mapping out experimental points. The calculated salt effect parameters of 9 ethanol–water-1–1 type electrolytic systems were in good agreement with the literature values within the wide range of liquid concentration.     

Anisotropic solvent model of the lipid bilayer. 1. Parameterization of long-range electrostatics and first solvation shell effects

A new implicit solvation model was developed for calculating free energies of transfer of molecules from water to any solvent with defined bulk properties. The transfer energy was calculated as a sum of the first solvation shell energy and the long-range electrostatic contribution. The first term was proportional to solvent accessible surface area and solvation parameters (σ(i)) for different atom types. The electrostatic term was computed as a product of group dipole moments and dipolar solvation parameter (η) for neutral molecules or using a modified Born equation for ions. The regression coefficients in linear dependencies of solvation parameters σ(i) and η on dielectric constant, solvatochromic polarizability parameter π*, and hydrogen-bonding donor and acceptor capacities of solvents were optimized using 1269 experimental transfer energies from 19 organic solvents to water. The root-mean-square errors for neutral compounds and ions were 0.82 and 1.61 kcal/mol, respectively. Quantification of energy components demonstrates the dominant roles of hydrophobic effect for nonpolar atoms and of hydrogen-bonding for polar atoms. The estimated first solvation shell energy outweighs the long-range electrostatics for most compounds including ions. The simplicity and computational efficiency of the model allows its application for modeling of macromolecules in anisotropic environments, such as biological membranes.     

Molecular dynamics study of the coordination sphere of trivalent lanthanum in a highly concentrated LiCl aqueous solution: a combined classical and ab initio approach

The first coordination sphere of trivalent lanthanum in a highly concentrated (14 M) lithium chloride solution is studied with a combination of classical molecular dynamics and density functional theory based first principle molecular dynamics. This method enables us to obtain a solvation shell of La3+ containing 2 chloride ions and 6 water molecules. After refinement using first principle molecular dynamics, the resulting cation-water and cation-anion distances are in very good agreement with experiment. The 2Cl- and the 6 water molecules arrange in a square antiprism around La3+. Exchange of water molecules was also observed in the first-principle simulation, with an intermediate structure comprising 7 water molecules stable for 2.5 ps. Finally, evaluation of dipole moments using maximally localized Wannier functions shows a substantial polarization of the choride anions and the water molecules in the first solvation shell of trivalent lanthanum.     

Potential of mean force of hydrophobic association: dependence on solute size

The potentials of mean force (PMFs) were determined for systems involving formation of nonpolar dimers composed of methane, ethane, propane, isobutane, and neopentane, respectively, in water, using the TIP3P water model, and in vacuo. A series of umbrella-sampling molecular dynamics simulations with the AMBER force field was carried out for each pair in either water or in vacuo. The PMFs were calculated by using the weighted histogram analysis method (WHAM). The shape of the PMFs for dimers of all five nonpolar molecules is characteristic of hydrophobic interactions with contact and solvent-separated minima and desolvation maxima. The positions of all these minima and maxima change with the size of the nonpolar molecule, that is, for larger molecules they shift toward larger distances. The PMF of the neopentane dimer is similar to those of other small nonpolar molecules studied in this work, and hence the neopentane dimer is too small to be treated as a nanoscale hydrophobic object. The solvent contribution to the PMF was also computed by subtracting the PMF determined in vacuo from the PMF in explicit solvent. The molecular surface area model correctly describes the solvent contribution to the PMF together with the changes of the height and positions of the desolvation barrier for all dimers investigated. The water molecules in the first solvation sphere of the dimer are more ordered compared to bulk water, with their dipole moments pointing away from the surface of the dimer. The average number of hydrogen bonds per water molecule in this first hydration shell is smaller compared to that in bulk water, which can be explained by coordination of water molecules to the hydrocarbon surface. In the second hydration shell, the average number of hydrogen bonds is greater compared to bulk water, which can be explained by increased ordering of water from the first hydration shell; the net effect is more efficient hydrogen bonding between the water molecules in the first and second hydration shells.     

Incorporating the excluded solvent volume and surface charges for computing solvation free energy

Gauss's law or Poisson's equation is conventionally used to calculate solvation free energy. However, the near‐solute dielectric polarization from Gauss's law or Poisson's equation differs from that obtained from molecular dynamics (MD) simulations. To mimic the near‐solute dielectric polarization from MD simulations, the first‐shell water was treated as two layers of surface charges, the densities of which are proportional to the electric field at the solvent molecule that is modeled as a hard sphere. The intermediate water was treated as a bulk solvent. An equation describing the solvation free energy of ions using this solvent scheme was derived using the TIP3P water model. © 2013 Wiley Periodicals, Inc.     

Ion–Dipole Interactions in Concentrated Organic Electrolytes

An algorithm is proposed for calculating the energy of ion–dipole interactions in concentrated organic electrolytes. The ion–dipole interactions increase with increasing salt concentration and must be taken into account when the activation energy for the conductivity is calculated. In this case, the contribution of ion–dipole interactions to the activation energy for this transport process is of the same order of magnitude as the contribution of ion–ion interactions. The ion–dipole interaction energy was calculated for a cell of eight ions, alternatingly anions and cations, placed on the vertices of an expanded cubic lattice whose parameter is related to the mean interionic distance (pseudolattice theory). The solvent dipoles were introduced randomly into the cell by assuming a randomness compacity of 0.58. The energy of the dipole assembly in the cell was minimized by using a Newton–Raphson numerical method. The dielectric field gradient around ions was taken into account by a distance parameter and a dielectric constant of ε=3 at the surfaces of the ions. A fair agreement between experimental and calculated activation energy has been found for systems composed of γ‐butyrolactone (BL) as solvent and lithium perchlorate (LiClO₄), lithium tetrafluoroborate (LiBF₄), lithium hexafluorophosphate (LiPF₆), lithium hexafluoroarsenate (LiAsF₆), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) as salts.     

How hydrophobic buckminsterfullerene affects surrounding water structure

The hydrophobic hydration of fullerenes in water is of significant interest as the most common Buckminsterfullerene (C60) is a mesoscale sphere; C60 also has potential in pharmaceutical and nanomaterial applications. We use an all-atom molecular dynamics simulation lasting hundreds of nanoseconds to determine the behavior of a single molecule of C60 in a periodic box of water, and compare this to methane. A C60 molecule does not induce drying at the surface; however, unlike a hard sphere methane, a hard sphere C60 solute does. This is due to a larger number of attractive Lennard-Jones interactions between the carbon atom centers in C60 and the surrounding waters. In these simulations, water is not uniformly arranged but rather adopts a range of orientations in the first hydration shell despite the spherical symmetry of both solutes. There is a clear effect of solute size on the orientation of the first hydration shell waters. There is a large increase in hydrogen-bonding contacts between waters in the C60 first hydration shell. There is also a disruption of hydrogen bonds between waters in the first and second hydration shells. Water molecules in the first hydration shell preferentially create triangular structures that minimize the net water dipole near the surface near both the methane and C60 surface, reducing the total energy of the system. Additionally, in the first and second hydration shells, the water dipoles are ordered to a distance of 8 A from the solute surface. We conclude that, with a diameter of approximately 1 nm, C60 behaves as a large hydrophobic solute.