Topic
Valency
About: Valency is a research topic. Over the lifetime, 1632 publications have been published within this topic receiving 26141 citations.
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TL;DR: RefReflection spectra of silicate glasses were measured in the spectral region 2 −13 eV as mentioned in this paper. And the correlation between the measured bands and the absorption wavelength calculated from Drude-Voigt dispersion formula is discussed.
Abstract: Reflection spectra of silicate glasses were measured in the spectral region 2–13 eV. The bands due to bridging oxygen were found at 11.6 and 10.4–9.5 eV. The bands for non-bridging oxygens were found in the region 8.8–4.9 eV. They shift to lower energy with increasing ionic radius for the low valency cations while they shift to higher energy with increasing ionic radius for the high valency cations. The correlation between the measured bands and the absorption wavelength calculated from Drude-Voigt dispersion formula is discussed.
1 citations
TL;DR: In this paper, the Faber-Ziman nearly free electron theory was applied to the liquid alloy resistivity with local chemical order and structural changes arising from chemical ordering were evaluated with the help of geometrical models.
Abstract: Variations of the liquid alloy resistivity with local chemical order are studied within the framework of Faber-Ziman nearly free electron theory. Electron-ion interactions are presented by Ashcroft's empty-core pseudopotentials and structural changes arising from chemical ordering are evaluated with the help of geometrical models. These calculations show that chemical ordering cannot produce resistivity variations larger than about 20% whatever the valency of the alloy components may be. It is therefore concluded that discrepancies between measured and calculated resistivities larger than 20% should be attributed to electronic rearrangements producing changes in the pseudopotentials, or to departures from the nearly free electron approximation.
1 citations
TL;DR: In this article, a newly discovered mechanism for superconductivity which seemingly explains the attraction responsible for Cooper pairing is presented, and the mechanism concerns charge fluctuations in parallel, neighboring planes, the interaction between two such fluctuations is a calculable function.
Abstract: The author discusses present knowledge of the valency of the various ions in high-T/sub c/ superconductors. He reports on a newly discovered mechanism for superconductivity which seemingly explains the attraction responsible for Cooper pairing. The mechanism concerns charge fluctuations in parallel, neighboring planes. The interaction between two such fluctuations is a calculable function. This mechanism could well explain the higher T/sub c/'s of the present generation ceramic superconductors. Being unrelated to any specific properties of copper oxide, beyond the specific value of {kappa}/sub F/, it should also be applicable to a variety of non-ceramic materials,of which artificially layered semiconductors and intercalation compounds are two families.
1 citations
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TL;DR: In this paper, electron diffraction diagrams showed a doubling along the b-axis and a quadruplication along the a-axis indicating that the excess oxygen is incorporated into the structure in an ordered way.
Abstract: Oxidized Pb 2 Sr 2 Y 0.5 Ca 0.5 Cu 3 O 8+ δ was studied by electron diffraction and neutron powder diffraction. The electron diffraction diagrams showed a doubling along the b -axis and a quadruplication along the a -axis indicating that the excess oxygen is incorporated into the structure in an ordered way. The oxygen content was determined from refinement of the neutron data and δ =1.2(1) was obtained. Calculation of bond valency sums for the cations shows that the bond valency sum for Cu in the CuO 2 layers in Pb 2 Sr 2 Y 0.5 Ca 0.5 Cu 3 O 8 decreases when the compound is oxidized, thereby explaining the lack of superconductivity in the oxidized compound.
1 citations