Erich Halwax

Comparison of the crystal structures of sodium orthosilicate, Na4SiO4, and sodium orthogermanate, Na4GeO4

The crystal structures of Na4SiO4 and Na4GeO4 are isotypic, despite a difference in coordination numbers: in Na4SiO4 only one of the four symmetrically independent sodium atoms is four coordinated, in Na4GeO4 two of them are.ZusammenfassungDie Kristallstrukturen von Na4SiO4 und Na4GeO4 sind isotyp, trotz eines Unterschiedes in den Koordinationszahlen: im Na4SiO4 ist nur eines der symmetrisch unabhängigen Natriumatome vierfach koordiniert, während es im Na4GeO4 derer zwei sind.

Die Kristallstruktur des Natriumorthogermanats, Na4GeO4

AbstractThe crystal structure of the title compound has been determined from single crystal X-ray diffraction data and refined toR=0.125. The unit cell is triclinic, space group P,

Die Kristallstruktur des Hexakaliumdigermanats, K6Ge2O7

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Morphology alterations during postsynthesis oxidation of Zn nanowires

(No. 2),a=5.688(1),b=5.701(1),c=8.583(1) Å, α=81.32(1), β=71.50(1), γ=67.95(1)° andZ=2. The structure consists of isolated [GeO4] tetrahedra linked together by four- and five-coordinate sodium atoms. Na4GeO4 is isostructural with Na4CoO4 (which has been described to be non-centrosymmetric and for which a centrosymmetric model is presented), K4GeO4, K4SnO4 and K4PbO4.

Die Kristallstruktur eines neuen Alkalidigermanats, Na4K2Ge2O7

Mullite, 3A12O3 · 2SiO2, was synthesized by heat-treating homogeneous sol-gel-derived mixtures of A12O3 and SiO2 taken in stoichiometric amounts. To reduce the mullitization temperature, sols containing γ-AlOOH and SiO2 nanoparticles (2 to 20 nm) were used in the preparation of the mullite precursors. A few samples were made using the products of hydrolysis of aluminum salts instead of the γ-AlOOH sol. The process parameters determining the homogeneity of the precursor mixtures were revealed. The preparation conditions ensuring mullite crystallization at temperatures between 1200 and 1250°C were found. The results are discussed in terms of the reaction between A12O3 and SiO2 during mullitization.

Analyses of a Green Copper Pigment Used in a Thirteenth-Century Wall Painting

The title compound is monoclinic, space group Pc (No. 7),a=6.549 (1),b=9.094 (1),c=11.426 (2) Å, β=126.78 (1)° andZ=2. Its crystal structure has been refined from 1 323 single crystal X-ray reflections toR=0.131. The structure of K6Ge2O7 is very similar to that of K6Co2O7 and K6Si2O7 both of which have been reported to be centrosymmetric, space group P21/c. While the angle at the bridging oxygen atom is 180° in the latter compounds, it is 157° in K6Ge2O7.

Water Denitration over a Pd–Sn/Al2O3 Catalyst

AbstractThe crystal structures of the title compounds have been determined by three-dimensional X-ray data (2 215 and 2 439 reflections, respectively) and refined to anR-value of 0.11 (0.10). The two compounds crystallize with very similar structures and have triclinic symmetry, space groupP