The Raman spectra of seven A(2)MWO(6) tungstate double perovskites are analysed. Ba(2)MgWO(6) is a cubic double perovskite with Fm3[combining macron]m symmetry and its Raman spectrum contain three modes that can be assigned in a straightforward manner. A fourth mode, the asymmetric stretch of the [WO(6)](6-) octahedron, is too weak to be observed. The symmetry of Ba(2)CaWO(6) is lowered to tetr...

In most practical implementations of the Gough-Stewart platform, the octahedral form is either taken as it stands or is approximated. The kinematics of this particular instance of the Gough-Stewart platform, commonly known as the octahedral manipulator, has been thoughtfully studied. It is well-known, for example, that its forward kinematics can be solved by computing the roots of an octic poly...

The structure of the Mg2+ complex of yeast enolase has been determined from crystals grown in solutions of poly(ethylene glycol) at pH 8.1. Crystals belong to the space group P2(1) and have unit cell dimensions a = 72.5 A, b = 73.2 A, c = 89.1 A, and beta = 104.4 degrees. There is one dimer in the asymmetric unit. The current crystallographic R-factor is 19.0% for all recorded data to 1.9 A res...

VIII VI IV Aenigmatite, Na4 (Fe2 +,Ti,Fe 3 +) 1 2 (SiFe 3 +) 12 0 40 , is a common constituent of sodium-rich alkaline igneous rocks and is classified as an open-branched single-chain silicate, whose structure is closely related to that of sapphirine. The first Mossbauer spectra of three valid aenigmatite specimens were recorded and the detailed crystal chemistry were obtained. In the Mossbauer...

High-pressure single-crystal X-ray diffraction method with precise control of hydrostatic conditions, typically with helium or neon as the pressure-transmitting medium, has significantly changed our view on what happens with low-density silica phases under pressure. Coesite is a prototype material for pressure-induced amorphization. However, it was found to transform into a high-pressure octahe...

The room-temperature crystal structures of six A(2)M(3+)M(5+)O(6) ordered perovskites have been determined from neutron and X-ray powder diffraction data. Ba(2)YNbO(6) adopts the aristotype high-symmetry cubic structure (space group Fm\overline 3m, Z = 4). The symmetries of the remaining five compounds were lowered by octahedral tilting distortions. Out-of-phase rotations of the octahedra about...

One fascinating high-pressure behavior of tetrahedral glasses and melts is the local coordination change with increasing pressure, which provides a structural basis for understanding numerous anomalies in their high-pressure properties. Because the coordination change is often not retained upon decompression, studies must be conducted in situ. Previous in situ studies have revealed that the sho...

A series of ammonium and tetraalkylammonium metal isothiocyanate salts of the type Q(y)[M(NCS)x] (M = Cr(III), x = 6, y = 3, Q = NH4(+), Me4N(+), Et4N(+), n-Bu4N(+); M = Mn(II), x = 6, y = 4, Q = Me4N(+); M = Mn(II), x = 5, y = 3, Q = Et4N(+); M = Fe(III), x = 6, y = 3, Q = Me4N(+), Et4N(+), n-Bu4N(+); M = Co(II), x = 4, y = 2, Q = n-Bu4N(+); M = Eu(III), Gd(III), Dy(III), x = 6, y = 3, Q = Bu4...

Lead-based relaxor ferroelectrics are key functional materials indispensable for the production of multilayer ceramic capacitors and piezoelectric transducers. Currently there are strong efforts to develop novel environmentally benign lead-free relaxor materials. The structural origins of the relaxor state and the role of composition modifications in these lead-free materials are still not well...

Copper(II) complexes of hexadentate ethylenediaminetetracarboxylic acid type ligands H(4)eda3p and H(4)eddadp (H(4)eda3p = ethylenediamine-N-acetic-N,N',N'-tri-3-propionic acid; H(4)eddadp = ethylenediamine-N,N'-diacetic-N,N'-di-3-propionic acid) have been prepared. An octahedral trans(O(6)) geometry (two propionate ligands coordinated in axial positions) has been established crystallographical...