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: The performed measurements indicate that, among the various structure-related influences on the valency, the atomic layer termination and the local oxygen content are most important.
Abstract: This article presents a (scanning) transmission electron microscopy (TEM) study of Mn valency and its structural origin at La 0.7 Sr 0.3 MnO 3/SrTiO3(0 0 1) thin film interfaces. Mn valency deviations can lead to a breakdown of ferromagnetic order and thus lower the tunneling magnetoresistance of tunnel junctions. Here, at the interface, a Mn valency reduction of 0.16 +/- 0.10 compared to the film interior and an additional feature at the low energy-loss flank of the Mn-L3 line have been observed. The latter may be attributed to an elongation of the (0 0 1) plane spacing at the interface detected by geometrical phase analysis of high-resolution images. Regarding the interface geometry, high-resolution high-angle annular dark-field scanning TEM images reveal an atomically sharp interface in some regions whereas the transition appears broadened in others. This can be explained by the presence of steps. The performed measurements indicate that, among the various structure-related influences on the valency, the atomic layer termination and the local oxygen content are most important.
15 citations
TL;DR: The role of valence interaction in the 1 : 1 and 1 : 2 complexes between Li +, Na +, Be 2+, Mg 2+ and CO and N 2 was qualitatively assessed using charge-density-related quantities such as charge transfer, the bond index of the cation-donor atom bond, the valency of interaction and the change in molecular valency calculated at the HF/6-31G ∗ //3-21G level as discussed by the authors.
Abstract: The role of valence interaction in the 1 : 1 and 1 : 2 complexes between Li + , Na + , Be 2+ , Mg 2+ and CO and N 2 was qualitatively assessed using charge-density-related quantities such as charge transfer, the bond index of the cation-donor atom bond, the valency of interaction and the change in molecular valency calculated at the HF/6–31G ∗ //3–21G level. It has been observed that the relative stability of the complexes can be rationalised on the basis of valence interaction. The molecular hardness parameters have also been calculated. The maximum hardness principle is found to be satisfied in the case of (MCO) n + -(MOC) n+ pairs, and the interaction between (MXY) n + and XY follows the qualitative prediction from the HSAB principle, where M n + is the metal ion and XY is the base.
15 citations
TL;DR: In this paper, a spectroelectrochemical study of [Ru2X9]n−, XCl, Br; n=1, 2, 3, 4 has been undertaken.
15 citations
Patent•
09 Dec 1999
TL;DR: In this paper, the authors proposed a method for the preparation of conjugates comprising of carbamate linkages, which is a type of molecules that can be expressed as a scaffold.
Abstract: This invention pertains generally to valency molecules, such as valency platform molecules which act as scaffolds to which one or more molecules may be covalently tethered to form a conjugate. More particularly, the present invention pertains to valency platform molecules which comprise a carbamate linkage (i.e., -O-C(=O)-N∫). In one aspect, the present invention pertains to valency platforms comprising carbamate linkages, which molecules have the structure of any one of Formulae I, II, or III, shown in Figure (1). In one aspect, the present invention pertains to valency platforms comprising carbamate linkages, which molecules have the structure of any one of Formulae IV, V, or VI, shown in Figure (8). The present invention also pertains to methods of preparing such valency platform molecules, conjugates comprising such valency platform molecules, and methods of preparing such conjugates.
15 citations
TL;DR: In this article, the authors analyzed the 3+ valency of transition metal ions in polycrystalline (Zn,Fe)O films with complementary theoretical and experimental studies.
Abstract: Dopants of transition metal ions in II-VI semiconductors exhibit native 2+ valency. Despite this, 3+ or mixed 3+/2+ valency of iron ions in ZnO was reported previously. Several contradictory mechanisms have been put forward for explanation of this fact so far. Here we analyze Fe valency in ZnO by complementary theoretical and experimental studies. Our calculations within the generalized gradient approximation (GGA+$U)$ indicate that the Fe ion is a relatively shallow donor. Its stable charge state is ${\mathrm{Fe}}^{2+}$ in ideal ZnO, however, the high energy of the (+/0) transition level enhances the compensation of ${\mathrm{Fe}}^{2+}$ to ${\mathrm{Fe}}^{3+}$ by nonintentional acceptors in real samples. Using several experimental methods like electron paramagnetic resonance, magnetometry, conductivity, excitonic magnetic circular dichroism, and magnetophotoluminescence we confirm the 3+ valency of the iron ions in polycrystalline (Zn,Fe)O films with the Fe content attaining 0.2%. We find a predicted increase of $n$-type conductivity upon the Fe doping with the Fe donor ionization energy of $0.25\ifmmode\pm\else\textpm\fi{}0.02$ eV consistent with the results of theoretical considerations. Moreover, our magneto-optical measurements confirm the calculated nonvanishing s,p-d exchange interaction between band carriers and localized magnetic moments of the ${\mathrm{Fe}}^{3+}$ ions in the ZnO, being so far an unsettled issue.
15 citations