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![Crystal structure of dioptase projected down [001]. A framework of copper oxide octahedra (yellow) screws around the c-axis with non-bonding axial water ligands (red) pointing towards empty channels. Six-membered silicate single rings are depicted in green.](profile/Hans-Otto-2/publication/313851306/figure/fig1/AS:489460862328832@1493707971164/Crystal-structure-of-dioptase-projected-down-001-A-framework-of-copper-oxide-octahedra.png)
Crystal structure of dioptase projected down [001]. A framework of copper oxide octahedra (yellow) screws around the c-axis with non-bonding axial water ligands (red) pointing towards empty channels. Six-membered silicate single rings are depicted in green.
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![Figure 1. Crystal structure of dioptase projected down [001]. A...](profile/Hans-Otto-2/publication/313851306/figure/fig1/AS:489460862328832@1493707971164/Crystal-structure-of-dioptase-projected-down-001-A-framework-of-copper-oxide-octahedra_Q320.jpg)
It is reported on growth of mm-sized single-crystals of the low-dimensional S = ½ spin compound Cu6(Ge,Si)6O18•6H2O by a diffusion technique in aqueous solution. A route to form Si-rich crystals down to possibly dioptase, the pure silicate, is discussed. Further, the assignment of dd excitations from UV-VIS spectra of the hexahydrate and the fully...
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... is isotypic to CuGeO 3 , but does not show the spin-Peierls transition, instead an antiferromagnetic ordering below T N = 7.9 K [7,8]. The rhombohedral title compound Cu 6 (Ge,Si) 6 O 18 ·6H 2 O represents a hexacyclo-germanate (silicate) that contains copper-oxygen spiral chains along the c-axis, which are connected (intra-chain) by edge- sharing dimers (Figure 1). This structure is interesting because it allows for a quantum phase transition between an anti-ferromagnetically ordered state and a quantum spin liquid [9]. ...
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... Special microbes are obviously able to create the needed conditions of the mineral-bearing solutions such as an optimal pH. We succeeded before in the synthesis of dioptase, Cu 6 (Ge 6 O 18 )·6H 2 O simply from solution and the partial replacement of Ge by Si towards pure dioptase, but could not even synthesize pure dioptase [8] [9] [10]. So the synthesis supported by microbes is a fine alternative for a large scale production with respect to the application of dehydrated dioptase as a catalyst [11] respectively its decomposition product orthorhombic CuSiO 3 [12] [13] [14] [15]. ...
Rare Tsumeb minerals such as sohngeite, Ga(OH) 3 respectively stottite, FeGe(OH) 6 , could not obtained synthetically as yet. We propose their synthesis via microbe activities. Such synthesis route was recently offered for dioptase, Cu 6 (Si 6 O 18)·6H 2 O, also a mineral of the Tsumeb paragenesis. It opens further technological applications by using thermally stable dehydrated dioptase or its nano-crystalline decomposition product CuSiO 3 (orthorhombic) as effective catalysts.
... Many years ago, we synthesized the pure germanate dioptase, ( ) • 6 [1] and succeeded in the partial substitution of Ge 4+ by Si 4+ in direction towards pure dioptase, ( ) • 6 [2], but could not make pure dioptase. So it was a great surprise to study the recent work of Rao and Krishna of a dioptase synthesis by using copper oxide (tenorite), quartz and microbes, even if important information and references are missing there [3]. ...
The microbially supported synthesis of • 6 (dioptase) by Rao and Krishna is very remarkable and opens further technological applications, when using the nano-crystalline decomposition product CuSiO 3 (orthorhombic) as an effective catalyst. The role of copper silicate nanotubes is acknowledged as catalysts respectively possible LED materials. A found structural relationship between chrysocolla and synthetic fibrous CuSiO 3 may show the way to solve the crystal structure of chrysocolla.
... Most important is the reciprocal duality between particles and waves [143]. [80] and were able to replace some Ge by Si, but could not make the pure silicate [127]. Dioptase, Cu 6 (Si 6 O 18 )·6H 2 O, is an emerald-colored gemstone, and its dehydration product with empty channels along the c-axis can be used as a catalyst [177]. ...
In his 85 th year of life, the author goes into the role of a witness of the past. He looks back at his childhood days during the Second World War over the student's days, and reports of his working life among geoscientists, crystallographers and physicists. He owes his scientific education to the well-known German professors Will Kleber at the Humboldt University Berlin, and later to Huge Strunz at the TU Berlin, who arranged international contacts to great Anglo-American as well as Russian colleagues. After a short industrial carrier with Didier-Werke AG, Wiesbaden, the author again did research at universities and met the amusing physicists at the University of Regensburg, and later the professorial community at the TU-Bergakademie Clausthal-Zellerfeld. Now, as a retired professor, he appreciates gratefully the contacts to and cooperation with some of the most pioneering physicists of our days from Egypt, China, Israel, and Russia. As a crystallographer, he worked on crystal syntheses (lead germanates, lead bismuth sulfides, ferroics, high-T c superconductors) as well as the determination of their crystal structures and physical properties, and constructed X-ray diffraction equipment, especially for powder diffraction measurements. Now he went into the field of cosmos physics and deals with unsolved problems around the electron, its spin and gyromagnetic factor. Nature is dominated by the famous number of the golden mean, you must only find out its secret. The motto of his continuing scientific activity is "Nature never puts all eggs in one basket" and "Science does not necessarily exclude politeness". Before the life power fades away forever, this contribution is constantly being continued, so that the reader may always see again what has been added.
... * The sixfold coordination of conichalcite is heavily distorted A more elaborated Table 11 including orbital energies Ds, Dq and Dt is given in the Appendix [56]. ...
... Table 11. Comparison of experimental and calculated excitation energies and orbital ones in cm -1 [56]. *) the broad band at 12500 cm -1 is proven to split into two bands at about 10700 cm -1 and 13200 cm -1 , respectively. ...
IIt is reported on a new cost-efficient ambient pressure synthesis of the Vesuvius mineral litidionite, KNaCuSi4O10, via a two-step synthesis route. X-ray powder data were recorded with our IP double-radius Guinier diffractometer. The lattice parameters of the triclinic compound with space group P¯1 are a = 9.7971(12) Å, b = 8.0149
(8) Å, c = 6.9679(7) Å, α = 114.027(4)°, β = 99.603(6)°, and γ = 105.678(6)°. From the X-ray powder data, one obtains by the Rietveld method structural parameters in agreement with those previously determined on single crystals of the mineral. In addition, a first UV-VIS spectrum of the light blue compound is presented, and antiferromagnetic super-exchange is discussed. The d-d excitations were assigned via bond strengths calculations and compared to excitations of similar compounds like dioptase. Some possible applications of the weather-proof synthetic pigment were indicated
Orthorhombic copper polysilicate, CuSiO3, is isotypic to the spin-Peierls compound CuGeO3 and represents a further example of a quasi-one-dimensional spin = ½ antiferromagnetic Heisenberg chain system. This is a representation of the first Raman and IR / FIR spectra for CuSiO3, measured at room temperature on polycrystalline samples. A comparison of the optical phonons, predicted by a factor group analysis, with those observed for the CuGeO3 prototype, is presented. A mode assignment for the silicate is given. Surface effects due to very small crystallite size may cause additional broad bands observed in the Raman spectrum of CuSiO3. From the analysis of the Davydov doublet an intralayer-to-interlayer bond strength of about 40 is derived for the silicate, which is about 20 % lower than for the isotypic germanate, allowing for different magnetic response at low temperature
