Showing papers on "Chemical binding published in 1977"

Chemical binding and energy band structure of vanadium monocarbide

Abstract: The band structure of vanadium monocarbide is calculated by the tight-binding method. A set of ten Boch of the 3d, 4s and 2s, 2p states of the free V and C atoms is used as the basis functions. The secular equation is solved at the 89 points of the 1/48th of the Brillouin zone. The denisty of states and partial density of states histograms are obtained. The populations of the orbitals show that about 0.5 electrons transfer from the carbon to the vanadium, orbitals. However, the distribution of the electron charge density points out that there are strong directional metalnon-mental bonds, in which carbon cannot be considered as a positive ion. [Russian Text Ignored].

Light and heavy element detection in thin sections of soils with the ion microprobe mass analyzer (IMMA).

Abstract: Previous research with the scanning electron microscope (SEM)-energy dispersive X-ray analyzer (EDXRA) and the electron microprobe analyzer (EMA), showed that the detection of light elements in thin sections of soils was problematic or even impossible. Consequently initial experiments were performed with the ion microprobe mass analyzer (IMMA). These preliminary investigations were carried out on a piece of root material in soil (containing both light and heavy elements) which has a 'clayey' appearance and is known as a clayified root (Parfenova et al., 1964). The presence of heavier elements in this sample was investigated by SEM-EDXRA prior to IMMA analysis. The results with the ion microprobe mass analyzer showed that all chemical elements could be analyzed in the plant fragment. Also much higher elemental detection sensitivities were found with IMMA as compared to SEM-EDXRA and EMA. This even allowed ion imaging of trace elements. High-quality ion images of both light and heavy elements could be obtained in much shorter exposure times than with SEM-EDXRA and EMA techniques. Furthermore by analysis of fragmentation ('fingerprint') spectra additional information was obtained with respect to the chemical binding of the analyzed elements. Due to these preliminary results IMMA offers full possibilities for microchemical analysis in situ of all important elements in soil specimens. This technique considerably increases possibilities in soil micromorphology. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Ladungszustand von Bor in Boriden der Übergangsmetalle

Abstract: Mit der Methode der Rontgen-Photoelektronen-Spektroskopie werden die Bindungsenergien von Rumpfelektronen in einer Gruppe von Boriden der ersten Ubergangsperiode gemessen. Es wird gezeigt, das in Boriden der Metalle, die am Anfang der Periode stehen, die Elektronendichte an den Bor-Atomen groser und in Boriden der Metalle, die am Ende der Periode stehen, kleiner ist als die Elektronendichte in reinem Bor. Das Ubergangsmetall ist in alien Fallen ein Donator. Die beobachtete Anderung des Ladungszustandes der Bor-Atome befindet sich im Einklang mit den vorhandenen Vorstellungen uber den Typ der chemischen Bindung in Boriden. The binding energies are measured of the core electrons of a series of borides of the first transition period using X-ray photoelectron spectroscopy. It is shown, that in the borides of metals from the beginning of the period the electron density at the bor atoms is larger and in the borides of the metals at the end of period is smaller than that one in pure bor. The transition metal is a donor in all the cases. The change of charge state of the bor atoms observed is in accordance with existing models of the type of chemical binding in borides.

[Qualitative analysis of the binding of fibrin in organic tissue (author's transl)].

Abstract: The binding energy (EB) of oxygen, sulphur and nitrogen was determined in highly concentrated fibrin, collagen, liver parenchyma and muscle tissue using photoelectron spectrometry. Fibrin was mixed with the collagen, liver or muscle homogenisate, with or without substitution of clotting factor XIII or additional inhibiton of fibrinolysis and the EB was determined again. Changes in the binding energy arise from an alteration in chemical binding. The present investigation showed that fibrin builds up new linkages in liver parenchyma and in collagen using nitrogen bonds and, additionally via a sulphur bond. After addition of fibrin stabilizing factor a new chemical link appeared between fibrin and collagen again through a nitrogen bond and, additionally via a sulphur bond. The inhibition of fibrinolysis produced a new oxygen linkage in all the examined substances (fibrin-tissue).

On the molecular polarizabiltties and intermolecular dispersion energies of deuterated hydrocarbons and related compounds

Abstract: An effort has been made to discuss the effect of replacing hydrogen by deuterium on electronic polarizabilities and intermolecular dispersion energies of sixteen organic compounds. Standard one-dimensional delta-potential function model of chemical binding has been used. It has been found that the model is capable enough to account for major electronic changes of (C−H) bond region in the form of probability amplitudes of electrons so as to explain H/D isotope effect on the polarizabilities (α M ) and intermolecular dispersion energies (E d).