Electron localization function from density components

This work addresses the decomposition of the Electron Localization Function (ELF) into partial density contributions using an appealing split of kinetic energy densities. Regarding the degree of the electron localization, the relationship between ELF and its usual spin‐polarized formula is discussed. A new polarized ELF formula, built from any subsystems of the density, and a localization function, quantifying the measure of electron localization for only a subpart of the total system are introduced. The methodology appears tailored to describe the electron localization in bonding patterns of subsystems, such as the local nucleophilic character. Beyond these striking examples, this work opens up opportunities to describe any electronic properties that depend only on subparts of the density in atoms, molecules, or solids. © 2016 Wiley Periodicals, Inc.     

Calculation of gas chromatographic retention indices of organic compounds from the boiling points of their structural analogs

The possibility of calculating gas chromatographic retention indices (1) is discussed. The indices are important parameters for chromatospectral identification of organic compounds from the boiling points of their structural analogs (T _b ^* ) using the linear logarithmic equation log I = a log T _b ^* + bA + c, where A are the structural parameters reflecting the one- to- one position of the compounds being compared in the corresponding taxonomic groups, including homologous series.     

Meaningful structural descriptors from charge density

This paper provides a short introduction to the basics of electron density investigations. The two predominant approaches for the modelling and various interpretations of electron density distributions are presented. Their potential translations into chemical concepts are explained. The focus of the article lies on the deduction of chemical properties from charge density studies in some selected main group compounds. The relationship between the obtained numerical data and commonly accepted simple chemical concepts unfortunately is not always straightforward, and often the chemist relies on heuristic connections rather than rigorously defined ones. This article tries to demonstrate how charge density analyses can shed light on aspects of chemical bonding and reactivity resulting from the determined bonding situation. Sometimes this helps to identify misconceptions and sets the scene for new unconventional synthetic approaches.     

The density,viscosity and structural properties of aqueous ethambutol hydrochloride solutions

Ethambutol (EMB) is a bacteriostatic antimycobacterial drug prescribed to treat tuberculosis. It is bacteriostatic against actively growing TB bacilli. The density and viscosity of aqueous ethambutol hydrochloride solutions have been studied at 298.15, 301.15 and 304.15 K and at different concentrations (0.255, 0.168, 0.128, 0.087, 0.041, and 0.023 mol dm⁻³). The apparent molar volume of these solutions for different temperatures and concentrations was calculated from the density data. The relative viscosities of drug solutions have been analysed by Jones-Dole equation. The limiting apparent molar volumes have been evaluated for different temperatures. The different properties have been used to study structural properties, structure formation and breaking properties of drug and solute-solvent interactions in solutions.     

Structural properties of ethanol-water solutions in presence of KOH from the density and viscosity data at 303 K

Apparent molar volumes of ethanol-water mixture of 10, 20, 40, and 60% (v/v) of ethanol in presence of different concentrations of potassium hydroxide were computed from measured densities of solvent mixtures and solutions at 303.15 K. Apparent molar volumes at infinite dilution have been evaluated using Masson’s equation. Viscosities of these ternary solutions were measured in order to characterize different systems. Relative strength of ion-ion and ion-solvent interactions in solutions has been interpreted from measured and estimated properties. Structure promoting and breaking properties of solute have been discussed.     

Calculation of origin-independent optical rotation tensor components in approximate time-dependent density functional theory

We outline an implementation of the origin-independent optical rotation tensor, which includes electric dipole-magnetic dipole and electric dipole-electric quadrupole polarizability. The method is based on approximate time-dependent density functional theory. We utilize time-periodic magnetic-field-dependent basis functions as well as a modified velocity-gauge formulation of dynamic polarizability tensors in order to obtain a gauge-origin independence. To ensure gauge-origin independence of the results within a given numerical accuracy, density fit coefficient derivatives are employed. A damping constant has been introduced into the linear response equations to treat both resonance and nonresonance regions of optical activity. We present calculations for trans-2,3-dimethyloxirane and derivatives thereof as well as calculations for androst-4,17-dien-3-one. In the Appendix, we derive the equivalence between the common-gauge origin and gauge-including atomic orbitals formulations for the optical rotation tensor in time-dependent DFT.     

Thermochemical investigations of associated solutions. 13. Calculation of anthracene-chlorobutane association parameters from measured solubility data

Experimental solubilities are reported for anthracene dissolved in binary solvent mixtures containing 1-chlorobutane with n-hexane, n-heptane, n-octane, cyclohexane, methylcyclohexane and isooctane at 25°C. Results of these measurements, combined with estimates for the excess Gibbs free energy of the binary solvents, are used to evaluate the equilibrium constant for a presumed anthracene-chlorobutane molecular complex from the Extended Nearly Ideal Binary Solvent model. A single equilibrium constant was needed to describe the experimental data to within an average deviation of about 0.7%. The calculated association constant varied slightly with inert hydrocarbon cosolvent, the values ranging from K _AC ^ϕ =2.5 for isooctane to K _AC ^ϕ =6.0 for the cyclohexane cosolvent.     

Calculation of pore size from adsorption data

Spherical pores (voids) with 1 to 6 round necks are used to estimate the probable disagreement between the average diameter and Kelvin equivalent size. This disagreement is due to the delay in irreversible capillary condensation in such pores [1, 2].     

Calculation of stability constants from photometric data

A method originally designed for the determination of stability constants by using a wedge calorimeter has been adapted to normal photometric measuring techniques. The calculations are simple and the method is especially suitable for use when the absorptivities of the absorbing species are unavailable because these species cannot be obtained alone in solution. Results of some determinations are given.     

Calculating excess volumes of binary solutions with allowance for structural differences between mixed components

Analytical dependences of a volume’s properties on the differences between the geometric structures of initial monosystems are obtained for binary systems simulated by a grain medium. The effect of microstructural parameter k (the ratio of volumes of molecules of mixed components) on the concentration behavior of the relative excess molar volume of different types of real binary solutions is analyzed. It is established that the contribution due to differences between the volumes of molecules and coefficients of the packing density of mixed components is ~80–100% for mutual solutions of n-alkanes and ~55–80% of the experimental value of the relative excess molar volume for water solutions of n-alcohols.     

Calculation of the energies and structural parameters of BaF2−MF2 fluorite-like solid solutions

Institute of Chemistry and Chemical and Metallurgical Processes, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 6, pp. 1149–1152, November–December, 1995.     

Calculation of the limiting activity coefficients of components in a solution from isothermal data on the equilibrium compositions of liquid and vapor phases

The method of calculating the limiting activity coefficients of components was developed and illustrated by a number of examples. Isothermal binary data on the compositions of the solution and vapor coexisting phases were fitted to the Porter, Margules, Van Laar, Wilson, Redlich-Kister, and NRTL interpolation equations. In this method, nonideality of a vapor phase is directly taken into account and the composition of the azeotrope in the system, if exists, may be calculated.     

Calculation of immersion enthalpy data from adsorption isotherms

The thermodynamic equations for the calculation of binary and ternary immersion data in excess formalism are presented. Immersion enthalpies and entropies of the n-hexane/n-octane, n-octane/n-tetradecane and n-hexane/n-tetradecane binary mixtures as well as the n-hexane/n-octane/n-tetradecane ternary mixture on activated carbon are calculated from the temperature dependence of adsorption isotherms. In order to evaluate the quality of the calculations, the calculated immersion enthalpies of the binary mixtures on activated carbon are compared with those that were measured calorimetrically. It is shown that phenomenological thermodynamics can be used successfully to predict calorimetric data on the basis of adsorption excess isotherms.     

由热重数据计算动力学参数

热重法(TG)是一种动态测量技术,可在程序升温或降温情况下对给定物质或体系提供一个连续的,以温度或时间为函数的重量变化曲线,所以由它跟踪反应能给出反应动力学的有关信息。这种非等温法与早期使用的等温法相比,有快速、连续和需要较少实验数据等优点,近年来在动力学研究方面得到广泛应用,但还只限于研究下列几种类型的简单