共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
《Journal of computational chemistry》2017,38(4):204-210
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. 相似文献
3.
4.
I. G. Zenkevich 《Journal of Structural Chemistry》1999,40(1):101-107
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. 相似文献
5.
Stalke D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(34):9264-9278
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. 相似文献
6.
S. D. Deosarkar A. L. Puyad T. M. Kalyankar 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(5):775-778
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. 相似文献
7.
S. D. Deosarkar M. L. Narwade 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(8):1423-1426
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. 相似文献
8.
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. 相似文献
9.
William E. Acree Jr. 《Journal of solution chemistry》1991,20(3):307-318
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. 相似文献
10.
11.
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]. 相似文献
12.
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. 相似文献
13.
E. S. Balankina 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(6):1157-1163
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. 相似文献
14.
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. 相似文献
15.
16.
A. N. Marinichev 《Russian Journal of Applied Chemistry》2009,82(11):1924-1927
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. 相似文献
17.
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. 相似文献
18.
19.