用路径数预测链烷的物理化学性质

路径数P~1, P~2, P~3等是表征链烷分子大小、支化度和形状等结构特征的重要参量。据此, 本文将P~1, P~2, P~3等作为独立参量, 用多元线性模型系统地研究了链烷结构-性质的定量关系, 预测了含2-9个碳原子链烷的原子化焓、标准生成焓、汽化焓、摩尔体积和摩尔折射度等多种物理化学性质。计算方法简单, 结构意义明确, 结果令人满意。     

Nanomechanical properties of mechanical double-layers: a novel semiempirical analysis

Force-displacement curves have been acquired with a commercial atomic force microscope on a thin film of poly(n-butyl methacrylate) on glass substrates. The film thickness is nonuniform, ranging in the measured area from 0 to 30 nm, and gives the possibility to survey the so-called "mechanical double-layer" topic, i.e., the influence of the substrate on the mechanical properties of the film in dependence of the film thickness. The stiffness and the deformation for each force-distance curve were determined and related to the film thickness. We were able to estimate the resolution of the film thickness that can be achieved by means of force-distance curves. By exploiting the data acquired in the present and in a previous experiment, a novel semiempirical approach to describe the mechanical properties of a mechanical double-layer is introduced. The mathematical model, with which deformation-force curves can be described, permits to calculate the Young's moduli of film and substrate in agreement with literature values and to determine the film thickness in agreement with the topography.     

Interrelation between thermodynamic similarity numbers and topological characteristics of the structure of organic molecules

The concept of the existence of nonpolar and low-polarity aprotic organic nonelectrolytes predominantly in the state of rotational motion in the liquid phase was used to show that the thermodynamic similarity numbers of several normal alkanes were interrelated with their molecular weights multiplied by the Wiener topological index raised to a power of 2/3.     

分子拓扑指数与链烷烃热力学性质的关系

碳原子个数N和路径数P3是表征链烷烃分子的大小、支化度和形状等结构特征的重要参数,引入烷烃所含甲基数的1.5次方M1和3次方M2表征取代基效应,运用多元线性模型研究了链烷烃标准生成焓、标准摩尔熵、标准生成吉布斯自由能等三种热力学性质与N,P3,M1和M2之间的定量关系,相关系数分别达到0.9993,0.9989和0.9972,标准偏差分别是2.2809kJ/mol,5.9093J/(mol·K),2.0585kJ/mol,其计算值与实验值非常接近.     

Surface activities and thermodynamic properties of novel cationic surfactants with hydroxymethyl group

A new series of cationic surfactants, N–alkyl–N,N–dimethyl–N–(p–(hydroxymethyl) benzyl) ammonium chlorides (p-DHBA-m), were synthesized and the structures were characterized by ¹HNMR, ¹³CNMR, FT–IR and ESI–MS. The surface activities, thermodynamic properties and aggregation behaviors of p-DHBA-m in aqueous solutions were respectively studied by means of surface tension, isothermal titration calorimetry and steady-state fluorescence methods. Thermodynamic parameters show that the micellization is an entropy-driven process. According to the fluorescence quenching method, the micelle aggregation numbers (N_agg) of p-DHBA-m were calculated and found that the increase of temperature or the elongation of alkyl chain length could lead to the reduction of the N_agg, respectively.     

Predicting bondons by Goldstone mechanism with chemical topological indices

The Goldstone symmetry breaking algorithm is applied on ?² and ?⁴ chemical field contributions weighted, respectively, by the sphericity and extreme‐sphericity topological indices to provide for stable chemical bonding in the high temperature regime, the typical mass for the bondon, and the associated quantum boson. The method is applied to a representative series of polycyclic aromatic hydrocarbons providing an aromaticity hierarchy comparable with the scale‐based on the chemical hardness; present calculations on the bondonic mass place the physical existence of that bosonic‐bondonic quantum particle in the range of a few GeV and 10^?22 s, as typical for negatively charged massive bosons. © 2014 Wiley Periodicals, Inc.     

Improvement of semiempirical response properties with charge-dependent response density

The present work outlines a new method for treatment of charge-dependent polarizability in semiempirical quantum models for use in combined quantum-mechanical/molecular mechanical simulations of biological reactions. The method addresses a major shortcoming in the performance of conventional semiempirical models for these simulations that is tied to the use of a localized minimal atomic-orbital basis set. The present approach has the advantages that it uses a density basis that retains a set of linear-response equations, does not increase the atomic-orbital basis, and avoids the problem of artificial charge transfer and scaling of the polarizability seen in related models that allow atomic charges to fluctuate. The model introduces four new atom-based parameters and has been tested with the modified neglect of differential overlap d-orbital Hamiltonian against 1132 molecules and ions and shown to decrease the dipole moment and polarizability errors by factors of 2 and 10, respectively, with respect to density-functional results. The method performs impressively for a variety of charge states (from 2+ to 2-), and offers a potentially powerful extension in the design of next generation semiempirical quantum models for accurate simulations of highly charged biological reactions.     

Polymeric composite with high thermodynamic properties

The possibility of obtaining a thermostable film composite material based on a mixture of polyvinylidenefluoride and polyamidebenzimidazole with NTsS piezoelectic ceramics as a filler was studied. Its thermal characteristics were determined and compared with those of separate polymers.     

Predicting of the thermodynamic properties for the ternary system Pb−Bi−Mg

R-function method for predicting the ternary thermodynamic properties from its binary ones was applied to the ternary system Pb−Bi−Mg. Activities, activity coefficients, partial and integral molar quantities for Pb, Bi and Mg for the quasibinary sections Pb-X (X=B, C, D, E, F) in the investigated ternary system Pb−Bi−Mg calculated by means ofR-function method are given in this paper. Also, it was determined that results obtained byR-function method reach a good agreement with the experimental results obtained by Oelsen calorimetry.     

改进的连接性指数用于链烷烃热力学性质与沸点研究

基于邻接矩阵和原子特征值qi，建立邻接指数^mQ,用^0Qr,^1Q与85种链烷烃的标准生成焓、标准生成自由能、标准熵和沸点关联，相关系数均在0.99以上，属于良好模型，与Randic指数的^mX比较，^mQ具有良好的性质相关性。     

Quantum proton transfer in hydrated sulfuric acid clusters: a perspective from semiempirical path integral simulations

We have carried out path-integral molecular dynamics simulations for hydrated sulfuric acid clusters to understand acid-dissociation and hydrogen-bonded structural rearrangement processes in these clusters from a quantum mechanical viewpoint. The simulations were performed using the PM6 semiempirical electronic structure level whose parameters were modified on the basis of the specific reaction parameters strategy so that relative energies of optimized structures, as well as water binding energies reproduce ab initio and density-functional theory calculations. We have found that the acid dissociation processes, first and second deprotonation, effectively occur in a hydrated cluster with a specific cluster size. The mechanisms of the proton-transfer processes were analyzed in detail and it was found that the distance between O in sulfuric acid and O in the proton-accepting water is playing an important role. We also found that the water coordination number of the poton-accepting water is important in the proton-transfer processes.     

Bulk properties and hydration numbers of ammonium nitrate and ammonium chloride in solution: A structural and thermodynamic analysis

The apparent volumes of the salts in the systems H₂O-NH₄Cl (298 K) and H₂O-NH₄NO₃ (273 K, 298 K, and 323 K) are reproduced with an accuracy of 0.03–0.01 cm³/mol by the equation ? = ?⁰ + Aw ₂ ^0.5 + Bw ₂, where w ₂ is the salt content (mass fractions). The study shows that there is a correspondence between the critical (for determining the hydration number) structural parameters-the intrinsic volume of the electrolyte and the volume of water in ion hydration shells-and the limiting (at w ₂ = 1) partial molar volumes of the components. The hydration numbers at infinite dilution are 6.9 for NH₄Cl at 298 K and 9.1, 6.7, and 6.4 for NH₄NO₃ at 273 K, 298 K, and 323 K. The water volume in ion hydration shells decreases in the sequence: No ₃ ^? , Cl^?, and NH ₄ ⁺ . The hydration numbers decrease with increasing salt concentration. The study shows that within a simpler model ? = ?⁰ + aw ₂ ^0.5 , the hydration numbers are temperature independent.     

用一个新的拓扑指数F~1研究AB~n型分子的性质

本文定义了一个新的拓扑指数F~1,并用F~1研究了AB~n型分子的标准生成焓、晶格焓、反应截面等性质。结果表明,F~1能有效地处理含氟的同构型无机分子体系和非同构型的无机体系。