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Phonon Spectra of A-15 Compounds and Ternary Molybdenum Chalcogenides
Abstract A survey is given on studies of the phonon spectra of several A-15 compounds by inelastic neutron scattering on polycrystalline samples. Comparison of the results for V3Si, V3Ge, V3Ga, Nb3Sn and Nb3Al at 297 K lead to the conclusion that the interatomic forces are to a good approximation the same for all compounds with 4.75 valence electrons but are reduced by about 20% for those with 4.5 valence electrons. For all compounds investigated we observe a softening of the phonon frequencies on cooling which is most pronounced for those materials with the highest Tc values. From a comparison of our results with the experimentally determined Eliashberg function of Nb3Sn we derive information about the energy dependence of the electron-phonon coupling function α2 (ω). From similar studies on the Chevrel phase superconductors PbMo6S8, SnMo6S8, Mo6Se8, and PbMo6Se8 the modes associated with displacements of the Pb(Sn)-atom could be uniquely identified. The results are discussed with respect to the molecular crystal model proposed recently for the Chevrel phases. For PbMo6S8 strong low temperature phonon softening has been observed which seems to occur mainly in modes with large Pb-displacements.
Phonon Spectra of A-15 Compounds and Ternary Molybdenum Chalcogenides
Abstract A survey is given on studies of the phonon spectra of several A-15 compounds by inelastic neutron scattering on polycrystalline samples. Comparison of the results for V3Si, V3Ge, V3Ga, Nb3Sn and Nb3Al at 297 K lead to the conclusion that the interatomic forces are to a good approximation the same for all compounds with 4.75 valence electrons but are reduced by about 20% for those with 4.5 valence electrons. For all compounds investigated we observe a softening of the phonon frequencies on cooling which is most pronounced for those materials with the highest Tc values. From a comparison of our results with the experimentally determined Eliashberg function of Nb3Sn we derive information about the energy dependence of the electron-phonon coupling function α2 (ω). From similar studies on the Chevrel phase superconductors PbMo6S8, SnMo6S8, Mo6Se8, and PbMo6Se8 the modes associated with displacements of the Pb(Sn)-atom could be uniquely identified. The results are discussed with respect to the molecular crystal model proposed recently for the Chevrel phases. For PbMo6S8 strong low temperature phonon softening has been observed which seems to occur mainly in modes with large Pb-displacements.
Phonon Spectra of A-15 Compounds and Ternary Molybdenum Chalcogenides
Schweiss, B. P. (Autor:in) / Renker, B. (Autor:in) / Schneider, E. (Autor:in) / Reichardt, W. (Autor:in)
01.01.1976
20 pages
Aufsatz/Kapitel (Buch)
Elektronische Ressource
Englisch
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