Showing papers by "Technical University of Dortmund published in 1972"
367 citations
TL;DR: In this article, the elastic displacement field of point defects in cubic crystals is calculated for weak anisotropy by second order perturbation theory and by a variational procedure.
Abstract: The elastic displacement field of point defects in cubic crystals is calculated for weak anisotropy by second order perturbation theory and by a variational procedure. The results are compared with numerical calculations for Cu. Further analytical approximations are given for the volume change in an infinite crystal and for the interaction energy of two point defects.
50 citations
TL;DR: In this article, the Raman spectra in aqueous solution of the ions MoOS 3 2 −, WOS 3 −, MoS 4 2 − and WS 4 2− have been measured.
28 citations
TL;DR: In this article, the i.r. and Raman spectra of the following compounds have been measured: Tl 3 VS 4, Tl3 NbS 4,Tl 3 TaS 4, Tl 2 VSe 4, tl 3 NbSe 4 and Tl 1 TaSe 4 with other cations are given.
28 citations
28 citations
TL;DR: In this article, the dispersion correction Δf′ of the forward atomic scattering amplitude is measured using an X-ray interferometer and a value close to the K-absorption edge is obtained.
Abstract: Employing an X-ray interferometer the dispersion correction Δf′ of the forward atomic scattering amplitude
$$f = z + \Delta f' + \Delta f''$$
of Nickel is measured using CuK
$$\bar \alpha $$
-radiation. Since
$$\lambda _{CuK\bar \alpha } /\lambda _{K - edge Ni} = 1.037 \approx 1$$
a value of Δf′ close to theK-absorption edge is obtained. The result
$$\Delta f\prime = - 1.45 \pm 7.6\% $$
is compared with experimental values by Doan, Kiessing and Lameris and Prins and also theoretical values by Honl, Dauben and Templeton and Cromer. The present value is considerably smaller than all theoretical estimates. It is the most accurate value measured so far and-except for the value measured by Kiessing-aggrees with the other experimental values within their (comparatively large) error limits.
22 citations
TL;DR: In this paper, Me 3 Si and Me 3 Ge were shown to be in equilibrium with the corresponding symmetrical mercurials with trialkylmetal methoxides R 3 MOMe.
21 citations
TL;DR: In this article, the preparation, properties, magnetic moments and structure of the new ions [Ni(WOS3)2]2−, [Co[WOS 3]2]-2− and [Zn[Zn2] 2− are reported.
Abstract: Es wird uber die Darstellung, Eigenschaften, magnetischen Momente und Struktur der Ionen [Ni(WOS3)2]2−, [Co(WOS3)2]2− und [Zn(WOS3)2]2− berichtet. Die Deutung der IR- und Elektronenspektren ergibt in allen Fallen eine Koordinierung uber Schwefel.
Transition Metal Chalcogen Compounds. The Monooxotrithiotungstate Anion WOS3)2]2− as Bidentate Ligand in Transition Metal Complexes
The preparation, properties, magnetic moments and structure of the new ions [Ni(WOS3)2]2−, [Co(WOS3)2]2− and [Zn(WOS3)2]2− are reported. From the interpretation of the i. r. and electronic spectra follows that only sulphur atoms are coordinating.
20 citations
TL;DR: In this article, die Infrarot-and Laser-Raman-Festkorperspektren von Sr 3 (VO 4 ) 2 und Ba 3 (V4 ) 2 aufgenommen und an Hand einer Site-Symmetrie-und Faktorgruppenanalyse interpretiert.
19 citations
TL;DR: Me 3 SiHgSiMe 3 (I) undergoes an S N 2 reaction with aryl azides with following radical steps, yielding N 2 and N -bissilylanilines as mentioned in this paper.
18 citations
TL;DR: The Substitutionsmuster von Benzolderivaten last sich festlegen mit Hilfe einer Kette von Fragen nach charakteristischen Ramanbanden, die durch den Frequenzbereich, the relative Intensitat and den Polarisationsgrad definiert werden as discussed by the authors.
Abstract: Das Substitutionsmuster von Benzolderivaten last sich festlegen mit Hilfe einer Kette von Fragen nach charakteristischen Ramanbanden, die durch den Frequenzbereich, die relative Intensitat und den Polarisationsgrad definiert werden. Besonders gut zu erkennen sind die mono-, die ortho-, meta- und para-disowie die 1,3,5-tri-substituierten Derivate. Die Aussagen aus den Ramanspektren scheinen uns zuverlassiger zu sein als die mit Hilfe der bekannten charakteristischen Infrarotbanden.
TL;DR: In this paper, the i.r. and Raman spectra of MoOSe 3 2−, WOSe3 2−, MoO 2 Se 2 2 2 −, WO 2 S 2 2 ¼, MoO O 2 Se ¼ 3, and WO O O 2 O ¼ 4 ¼ ¼ were reported and verified with simple MVFF model calculations.
TL;DR: In this paper, it is shown that stannyl radicals are capable of reversible addition across the azo double bond, which is the only reaction in cases 1−5 and 6−12, however, an SH2γ displacement predominates.
Abstract: Stannylradikale R3Sn⋅ konnen 1-Aryl-triazene 1–12 and N3 unter Bildung von Stannylaminen angreifen. Dabei wird in einer SH2α-Reaktion die Arylazogruppe verdrangt (“induzierter Zerfall”) und spaltet N2 ab. Dies tritt bei 1–5 ausschlieslich ein. Bei 6–12, die an N3 einen als Radikal stabilisierten Substituenten tragen, uberwiegt jedoch eine SH2γ-Reaktion. Der Angriff eines Stannylradikals an N1 verdrangt dabei den Substituenten von N3. Es entstehen Trialkylstannyl-triazene 10–12, 15 und 20, durch Pentakoordination am Zinnatom uberraschend stabil. H-Abstraktion aus dem Organozinnhydrid stabilisiert die abgespaltenen Molekulfragmente. Die hinterbleibenden Stannylradikale setzen die Reaktionskette fort. Hydrostannierung der Azodoppelbindung wird nicht beobachtet. Es wird gezeigt, das sich Stannylradikale reversibel an die Azodoppelbindung addieren konnen.
Reactions of Short-Life Radicals, VIII. Radical Substitution at the Nitrogen Atom: Reactions of 1-Aryltriazenes with Organotin Hydrides
Stannyl radicals react with 1-aryltriazenes 1–12, attacking N3 and forming stannyl amines. The reaction proceeds by an SH2α mechanism; the arylazo group is displaced (“induced degradation”) and splits off N2. This is the only reaction in cases 1–5. With 6–12, however, an SH2γ displacement predominates. Here, substituents bound to N3 are able to form fairly well stabilized radicals. Stannyl radicals attack N1, displace the substituent from N3 and form trialkylstannyl triazenes 10–12, 15, 20, which are surprisingly stable because of pentacoordination at the tin atom. The free-radical fragments abstract hydrogen from the tin hydride, releasing new stannyl radicals, which propagate the chain reaction. Hydrostannation of the azo group has not been observed. It is shown that stannyl radicals are capable of reversible addition across the azo double bond.
TL;DR: The development of semi-empirical band structure theory over the last decade is surveyed in this article, where the authors describe methods based on the use of pseudopotentials and ad hoc potentials taken from atomic calculations.
Abstract: The development of semi-empirical band structure theory over the last decade is surveyed. Methods are described that are based on the use of pseudopotentials and ad hoc potentials taken from atomic calculations. Self-consistent calculations are excluded. Stress is laid upon a generalized view, showing interrelationships between different methods. The connection with experiment is made explicit and a survey of results is given that is representative of the state of the art.
TL;DR: In this article, the high low frequency separation method is used to describe the different approximation methods for solving n = 2 secular determinants, and an extension of this procedure to higher-order determinants is indicated.
TL;DR: In this article, the current distribution in a shielded superconducting film was investigated theoretically in the case of a thin and wide film on the basis of London's equation, and the exact distribution was obtained for a wide and thin film.
Abstract: The current distribution is investigated theoretically in a shielded superconducting film, which is a film deposited on an insulating superconducting ground plate. An exact result is obtained in the case of a thin and wide film on the basis of London's equation.
TL;DR: In this paper, the authors developed a theory of an itinerant antiferromagnet, which is a generalization of previous theories by taking into account more general band structures and homogeneous magnetic fields.
Abstract: In this contribution, we develop a theory of an itinerant antiferromagnet, which is a generalization of previous theories by taking into account more general band structures and homogeneous magnetic fields. As a result we obtain several phase transitions at finite magnetic fields, and also other thermodynamic properties are changed compared with these previous theories.
TL;DR: In this article, a constraint based on Green's function analysis of the vibrations of molecules and the L matrix approximation method for the calculation of force constants is proposed and the mathematical properties are discussed.
TL;DR: A critical survey of the method of Green's function analysis of the vibrations of substituted and perturbed molecules is made in this paper, where a method of obtaining the various molecular constants is outlined.
TL;DR: In this paper, the i.r. spectra of gaseous 116 SnCl 4 and 124SnCl 4 has been measured and the exact force field of SnCl4 has been calculated and compared with exact force fields, which were calculated using other additional data.
TL;DR: Adrenalin, Noradrenalin and 3,4-Dihydroxyphenylalanin (Dopa) lassen sich automatischfluorimetrisch in einem Analysensystem (nach Wisser) nach der Trihydroxyindolmethode bestimmen as mentioned in this paper.
Abstract: Adrenalin, Noradrenalin, 3,4-Dihydroxyphenylalanin (Dopa) und die Summe Adrenalin + Noradrenalin als Gesamtkatecholamine lassen sich automatisch-fluorimetrisch in einem Analysensystem (nach Wisser) nach der Trihydroxyindolmethode bestimmen.
01 Jan 1972
TL;DR: In this paper, the theory of the electronic density of states and the optical absorption of structurally disordered solids is briefly reviewed and two complementary descriptions of the problem are considered.
Abstract: The theory of the electronic density of states and the optical absorption of structurally disordered solids is briefly reviewed. Two complementary descriptions of the problem are considered: The tight binding approach allows for the evaluation of the general properties of the electronic spectrum. The nearly free electron approximation yields a method for calculating the electronic properties of real amorphous systems. The structure dependence of the electronic density of states and the optical absorption spectrum of covalent bonded semiconductors is investigated. Results are presented for tetrahedrally bonded semiconductors and the chain structures selenium and tellurium. A comparison between the results of different theoretical approaches and experimental data is performed.
TL;DR: In this article, the Raman spectra of (NH4)2 with 92Mo and 100Mo isotope shifts were measured and the M0O2S2 force constants were determined with approximate force fields.
TL;DR: In this paper, an isotroper viskoelastischer modellkorper wird in der Weise konstruiert, das man Teilspannungen mit Hilfe eines Potenzspektrums superponiert.
Abstract: Ein isotroper viskoelastischer Modellkorper wird in der Weise konstruiert, das man Teilspannungen mit Hilfe eines Potenzspektrums superponiert. Diese Teilspannungen sind dabei entsprechend einer vonZaremba,Fromm undDeWitt verallgemeinerten Maxwell-Gleichung mit der Deformation verknupft. Ein solcher Korper verhalt sich in stationaren Scherstromungen wie eineOstwald-De Waele-Flussigkeit. In Dehnstromungen zeigt er dagegen weder ein flussigkeits-noch ein festkorperartiges, sondern ein intermediares Verhalten: Im Spannversuch (d. h. beim Anwenden einer konstanten Dehngeschwindigkeit) wachsen die Spannungen unbegrenzt, beim Relaxationsversuch (d. h. beim Anhalten dieses Dehnvorgangs) klingen sie vollstandig ab. Auch in der Scherstromung mit zeitabhangiger Scherung treten ungewohnliche Phanomene auf: Im Spannversuch wird der stationare Endzustand uber langsam abklingende Schwingungen angenahert. Im Relaxationsversuch scheint der Korper zeitweilig die Gesamtscherung des vorausgegangenen Spannversuchs zu vergessen, erinnert sich aber spater aufs neue daran. Derartige Absonderlichkeiten spiegeln sich besonders stark im zeitlichen Verlauf des Verdrehungswinkels e wider, um den die Eigenrichtungen des Spannungszustandes gegenuber denjenigen des Deformationsgeschwindigkeitszustandes verdreht sind.
TL;DR: Me3SiHgSiMe3 (I) adds to the azo groups of azodiethyldicarboxylate, 2,2′-azodipyridine and azobenzene yielding N,N′ -bissilylated hydrazo compounds as mentioned in this paper.
Abstract: Me3SiHgSiMe3 (I) adds to the azo groups of azodiethyldicarboxylate, 2,2′-azodipyridine and azobenzene yielding N,N′ -bissilylated hydrazo compounds. N-Heterocycles are reductively N-silylated. Reactions where molar ratios of 1 2 are taken, lead in the case of pyridine, 2- and 4-methylpyridine, and quinoline to the corresponding N,N′-bissilyl-1,1′,4,4′-tetrahydro-4,4′-dipyridines, and in the case of isoquinoline to N,N′-bissilyl-1,1′,2,2′-tetrahydro-1,1′-diisoquinoline. The 1 1 molar reaction with pyrazine leads to N,N-bissilyl-1,4-dihydropyrazine. In all cases (I) apparently behaves as a nucleophile; the mercurated intermediates are thermally unstable and form (in part after symmetrisation) the final products mentioned. The yields are high. Me3SiCl and Li react in THF with some pyridines under certain conditions to give the same products as are given by (I).