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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: In this paper , the spatial distribution of the electron equivalents breaks the symmetry of isotropic programmable atom equivalents, analogous to the anisotropic distribution of valence electrons or coordination sites around a metal atom, leading to a set of well defined coordination geometries and access to three new low-symmetry crystalline phases.
Abstract: Colloidal crystal engineering of complex, low-symmetry architectures is challenging when isotropic building blocks are assembled. Here we describe an approach to generating such structures based upon programmable atom equivalents (nanoparticles functionalized with many DNA strands) and mobile electron equivalents (small particles functionalized with a low number of DNA strands complementary to the programmable atom equivalents). Under appropriate conditions, the spatial distribution of the electron equivalents breaks the symmetry of isotropic programmable atom equivalents, akin to the anisotropic distribution of valence electrons or coordination sites around a metal atom, leading to a set of well-defined coordination geometries and access to three new low-symmetry crystalline phases. All three phases represent the first examples of colloidal crystals, with two of them having elemental analogues (body-centred tetragonal and high-pressure gallium), while the third (triple double-gyroid structure) has no known natural equivalent. This approach enables the creation of complex, low-symmetry colloidal crystals that might find use in various technologies.
27 citations
TL;DR: In this paper, the authors applied the bond valence method to determine the oxidation states of the Ce ion at the various site symmetries of the crystals, including cerium dioxide and the two sesquioxides along with some selected intermediate phases.
Abstract: We have applied the bond valence method to cerium oxides to determine the oxidation states of the Ce ion at the various site symmetries of the crystals. The crystals studied include cerium dioxide and the two sesquioxides along with some selected intermediate phases which are crystallographically well characterized. Our results indicate that cerium dioxide has a mixed-valence ground state with an f-electron population on the Ce site of 0.27 while both the A- and C-sesquioxides have a nearly pure f1 configuration. The Ce sites in most of the intermediate oxides have nonintegral valences. Furthermore, many of these valences are different from the values predicted from a naive consideration of the stoichiometric valence of the compound.
27 citations
TL;DR: In this paper, the properties of pure and mixed perovskite crystals for RE 3+ =Y 3+, Gd 3+ and Lu 3+ have been investigated using γ-ray induced centres in the crystals.
26 citations