Densities,speeds of sound,excess volumes and viscosities of binary mixtures of mtbe with tetralin and decalin at 303.15 k

Measurements of densities, speeds of sound, excess volumes and viscosities of binary mixture of methyl tert-butyl ether with tetralin and decalin are reported at 303.15?K over the entire range of composition. Excess volumes are measured using batch dilatometer technique. Sound speeds are obtained using ultrasonic interferometer. Densities are computed from excess volume data. Isentropic compressibilities are derived from density and sound speed data. Speeds of sound are evaluated on the basis of Jacobson's free length theory and Schaff's collision factor theory. The predicted values are in good agreement with the experimental results. The viscosity data are analysed on the basis of corresponding states approach. Excess volumes and deviation in isentropic compressibilities are negative and deviation in viscosities are positive over the entire composition range. The experimental results are discussed in terms of possible molecular interactions between unlike molecules.     

Kirkwood-Buff integrals and density fluctuations in aqueous solution of caffeine

The Kirkwood-Buff theory is applied to caffeine aqueous solution. The integrals of radial distribution functions are calculated from the osmotic coefficient, density and sound velocity data at 25°C. The results are discussed in terms of density fluctuations of two components and the correlation between them. It is found that the concentration dependence of Kirkwood-Buff integrals reflects the association tendency of caffeine and its strong influence on the properties of the solvent.     

Volumetric,acoustic, optical and spectroscopic studies of binary mixtures of the ionic liquid, 1-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide and diethyl carbonate

The properties, density, speed of sound and refractive index of ‘IL’ [Bmim][NTf2], diethyl carbonate and their binary mixtures are measured over the whole composition range as a function of temperature between 303.15 and 323.15 K at atm. pressure. These values are used to calculate the excess molar volumes, excess partial molar volumes, partial molar volumes at infinite dilution, excess isentropic compressibility, free length, speeds of sound and isobaric thermal expansion coefficient for the mixture. Various rules were used to predict the refractive indices and the data have been compared with the experimental results. These excess properties are fitted to the Redlich–Kister type equation to obtain the binary coefficients and the standard deviations. A qualitative analysis of these parameters indicates strong intermolecular interactions and the interaction increases with the increase in temperature. This was further supported by IR spectroscopy. In addition, analysis of data of the mixture was done through the Prigogine–Flory–Patterson theory.     

Magnetism and Sound Velocities of Iron Carbide （Fe3C） under Pressure

The elastic property and sound velocity of FeaC under high pressure are investigated by using the spin-polarized generalized gradient approximation within density-functional theory. It is found that the magnetic phase transition from the ground ferromagnetic （FM） state to the nonmagnetic （NM） state occurs at ～73 GPa. Based on the predicted Hugoniot of Fe3C, we calculate the sound velocities of FM-Fe3C and NM-Fe3C from elastic constants. Compared with pure iron, NM-FeaC provides a better match of compressional and shear sound velocities with the seismic data of the inner core, supporting carbon as one of the light elements in the inner core.     

Methods for calculating of the speed of sound in layering saline binary mixtures

We develop a method for calculating the speed of sound and the compressibility of layered saline melts based on two approximations of the statistical theory of many-sorted ion systems, predicting the existence of an immiscibility cupola. Good agreement is observed between the kind of temperature dependency of the speed of sound in the monophase and diphase areas and experimental data both in a modified Debye-Hückel theory and in a mean spherical approximation. Improvement in the quantitative predictions for the mean spherical approximation with specific permittivity estimated on the basis of experimental data on the refractive index is established.     

聚酯机织物吸声性能研究

分析了聚酯纤维机织物在背后有空气层时的吸声频谱规律以及测试时材料对管内驻波的影响。将传统吸声材料的Zwikker和Costen理论、毛细管吸声理论、微穿孔板吸声理论以及穿孔板共振吸声理论应用于材料特性分析,发现Zwikker和Costen理论可以定性的给出与实测情况相吻合的材料吸声系数随频率的变化规律。穿孔板共振吸声理论可以推导出与实测情况很接近的材料第一吸声峰值频率。另外,毛细管吸声理论和微穿孔板吸声理论不适合于背后有空气层时聚酯纤维织物的吸声情况。     

A general,recursive, and open‐ended response code

We present a new implementation of a recent open‐ended response theory formulation for time‐ and perturbation‐dependent basis sets (Thorvaldsen et al., J. Chem. Phys. 2008, 129, 214108) at the Hartree–Fock and density functional levels of theory. A novel feature of the new implementation is the use of recursive programming techniques, making it possible to write highly compact code for the analytic calculation of any response property at any valid choice of rule for the order of perturbation at which to include perturbed density matrices. The formalism is expressed in terms of the density matrix in the atomic orbital basis, allowing the recursive scheme presented here to be used in linear‐scaling formulations of response theory as well as with two‐ and four‐component relativistic wave functions. To demonstrate the new code, we present calculations of the third geometrical derivatives of the frequency‐dependent second hyperpolarizability for HSOH at the Hartree–Fock level of theory, a seventh‐order energy derivative involving basis sets that are both time and perturbation dependent. © 2014 Wiley Periodicals, Inc.     

Theoretical assessment of structural,mechanical, and thermodynamic properties of Pd2Al

The physical properties, namely structural, mechanical, and thermodynamic properties, of Pd₂Al intermetallic compound were explored through first-principles calculations within the framework of density functional theory. The calculated lattice constants were consistent with the available experimental data. The calculated elastic constants revealed that Pd₂Al was mechanically stable. By the predicted elastic constants, several related properties, namely Cauchy pressures, shear anisotropy factors, directional Young's modulus, bulk, shear and Young's moduli, the ratio of K/G, Vickers hardness, sound velocity, and minimum thermal conductivity for Pd₂Al were evaluated. According to the calculated results, it was found that Pd₂Al possesses a highly anisotropic feature and behaves in a ductile manner with low stiffness. Finally, temperature-dependence of thermodynamic properties, namely Debye temperature and heat capacity, were also evaluated through the quasi-harmonic Debye model.     

Comparative studies on the structures,infrared spectrum,and thermodynamic properties of phthalocyanine using ab initio Hartree–Fock and density functional theory methods

The molecular structure, vibrational spectrum, standard thermodynamic functions, and enthalpy of formation of free base phthalocyanine (Pc) have been studied using the density functional theory B3LYP procedure, as well as the ab initio Hartree–Fock method. Various basis sets 3‐21G, 6‐31G*, and LANL2DZ have been employed. The results obtained at various levels are discussed and compared with each other and with the available experimental data. It is shown that calculations performed at the Hartree–Fock level cannot produce a reliable geometry and related properties such as the dipole moment of Pc and similar porphyrin‐based systems. Electron correlation must be included in the calculations. The basis set has comparatively less effect on the calculated results. The results derived at the B3LYP level using the smaller 3‐21G and LANL2DZ basis sets are very close to those produced using the medium 6‐31G* basis set. The geometry of Pc obtained at the B3LYP level has D_2h symmetry and the diameter of the central macrocycle is about 4 Å. The enthalpy of formation of Pc in the gas phase has been predicted to be 1518.50 kJ/mol at the B3LYP/6‐311G(2d,2p)//B3LYP/6‐31G* level via an isodesmic reaction. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Excess Volumes,Isentropic Compressibilities and Viscosities for Binary Mixtures of <Emphasis Type="Italic">tert</Emphasis>-Butylamine with Alkyl Acetates at 303.15 K

The data on excess volume (V ^E), density (ρ), viscosity (η) and speeds of sound (u) for the binary mixtures of tert-butylamine (TBA) + methyl acetate (MA), + ethyl acetate (EA), + butyl acetate (BA) and + isoamyl acetate (IAA) at 303.15 K were measured experimentally over the entire range of composition. Speeds of sound were evaluated using Jacobson’s free length theory (FLT) and Schaaffs’ collision factor theory (CFT). The viscosity data were analyzed on the basis of the corresponding states approach and the Grunberg and Nissan treatment. The experimental results for excess volume, deviation in isentropic compressibility and deviation in viscosity were discussed in terms of molecular interactions between unlike molecules. A Redlich-Kister type equation was used to fit the experimental data on excess volume, deviation in compressibility and deviation in viscosity.     

Lectures for chemists on statistics. I. Belief,probability, frequency,and statistics: decision making in a floating world

A brief account on the development of probability theory and statistics is given. These subjects may help the chemist to interpret the information content of his experimental data. Their source and validity, however, is often unclear. A series of papers, of which this is the first, intends to present a clearer view by illustrating the origin of the data-analysis tools. The major figures in this field are mentioned, their achievements presented and the mutual links outlined. The intention is the provision of a common basis for the discussion of statistical aspects relevant to metrology in chemistry. The chemist should see probability theory and statistics as tools to assist in the daily practice of data interpretation to arrive at an objective conclusion.     

Electronic structure, chemical bonding, and geometry of pure and Sr-doped CaCO3

The electronic structure, chemical bonding, geometry, and effects produced by Sr-doping in CaCO(3) have been studied on the basis of density-functional theory using the VASP simulation package and molecular-orbital theory utilizing the CLUSTERD computer code. Two calcium carbonate structures which occur naturally in anhydrous crystalline forms, calcite and aragonite, were considered in the present investigation. The obtained diagrams of density of states show similar patterns for both materials. The spatial structures are computed and analyzed in comparison to the available experimental data. The electronic properties and atomic displacements because of the trace element Sr-incorporation are discussed in a comparative manner for the two crystalline structures.     

Volumetric and acoustic behaviour of systems containing n-hexane,or n-heptane and isomeric chlorobutanes

Densities and speeds of sound at atmospheric pressure and temperatures of (283.15, 298.15, and 313.15) K for the binary mixtures formed by n-hexane or n-heptane with isomeric chlorobutanes were determined. Afterwards excess volumes, excess isentropic compressibilities and excess speeds of sound were calculated using the experimental data and correlated using a Redlich–Kister type equation. Finally, the results were studied using the Prigogine–Flory–Patterson theory showing excellent predictions for speed of sound and isentropic compressibility values of mixtures as well as a strong influence of the interactional contribution term for excess volume values.     

From Oligo(Phenyleneethynylene) Monomers to Supramolecular Helices: The Role of Intermolecular Interactions in Aggregation

Supramolecular helices that arise from the self-assembly of small organic molecules via non-covalent interactions play an important role in the structure and properties of the corresponding materials. Here we study the supramolecular helical aggregation of oligo(phenyleneethynylene) monomers from a theoretical point of view, always guiding the studies with experimentally available data. In this way, by systematically increasing the number of monomer units, optimized n-mer geometries are obtained along with the corresponding absorption and circular dichroism spectra. For the geometry optimizations we use density functional theory together with the B3LYP-D3 functional and the 6–31G** basis set. For obtaining the spectra we resort to time-dependent density functional theory using the CAM-B3LYP functional and the 3–21G basis set. These combinations of density functional and basis set were selected after systematic convergence studies. The theoretical results are analyzed and compared to the experimentally available spectra, observing a good agreement.     

Speed of sound and isentropic compressibilities of nonelectrolyte liquid mixtures. I. Binary mixtures containingp-dioxane

The speed of sound was measured for mixtures of p-dioxane with cyclohexane, n-hexane, benzene, toluene, carbon tetrachloride, chloroform, 1,1,2,2-tetrachloroethane, pentachloroethane and ethyl acetate over the whole mole fraction range at 30°C. These data were combined with densities and molar volumes to obtain isentropic compressibilities and Rao's molar sound functions. Excess isentropic compressibilities and excess speeds of sound have also been calculated. The behavior of the present mixtures is discussed in terms of possible molecular interactions and the Prigogine-Flory-Patterson theory of liquid mixtures.     

3-羟基哒嗪及其CH3,NO2和CI取代衍生物质子转移过程的理论研究

用密度泛函理论(DFT)B3LYP方法,在6-311+G*基组下,对3-羟基哒嗪及其CH3,NO2和Cl取代衍生物分子醇式和酮式结构互变异构化反应进行了研究,优化化合物的几何构型,寻找反应的过渡态,通过振动分析和内禀反应坐标(IRC)分析加以证实,计算了反应的活化能.结果表明,3(2H)-哒嗪酮及其带取代基的衍生物不论是单体,还是相对应的二聚体,比其相对应的异构体能量低,表明在通常情况下是以3(2H)-哒嗪酮及其衍生物形式稳定存在的,这与前人通过实验数据对3-羟基哒嗪互变异构体的比率进行预测的结果是一致的.根据计算结果讨论了异构化反应的机理.     

3-羟基哒嗪及其CH3，NO2和Cl取代衍生物质子转移过程的理论研究

用密度泛函理论(DFT)B3LYP方法,在6-311 G*基组下,对3-羟基哒嗪及其CH3,NO2和Cl取代衍生物分子醇式和酮式结构互变异构化反应进行了研究,优化化合物的几何构型,寻找反应的过渡态,通过振动分析和内禀反应坐标(IRC)分析加以证实,计算了反应的活化能.结果表明,3(2H)-哒嗪酮及其带取代基的衍生物不论是单体,还是相对应的二聚体,比其相对应的异构体能量低,表明在通常情况下是以3(2H)-哒嗪酮及其衍生物形式稳定存在的,这与前人通过实验数据对3-羟基哒嗪互变异构体的比率进行预测的结果是一致的.根据计算结果讨论了异构化反应的机理.     

Computational studies of bond dissociation energies, ionization potentials, and heat of formation for NH and NH+. Are hybrid density functional theory methods as accurate as quadratic complete basis set and Gaussian-2 ab initio methods?

Ionization potentials, bond dissociation energies, and heat of formation for NH and NH⁺ molecular species as well as for their elements were computed with highly reliable quadratic complete basis set and Gaussian-2 ab initio methods. The results are compared with experimental results and the assurance of these ab initio approaches is assessed. The same studies were also performed with three hybrid density functional methods (B3LYP, B3P86, and B3PW91) in combination with variously sized basis sets. The computational results are discussed in light of density functional theory reliability for exploring the potential energy of small polar molecular systems. Received: 21 July 1997 / Accepted: 8 December 1997