Yu. K. Kabalov

New hilgardite-group polyborate Pb2[B5O9]Br with high optical nonlinearity

New anhydrous lead borate Pb2[B5O9]Br (sp. gr. Pnn2) was synthesized by the hydrothermal method. The second harmonic generation from polycrystalline samples of Pb2[B5O9]Br is characterized by a higher signal than that observed in powdered LiB3O5. The crystal structure of the new hilgardite-group compound was refined by the Rietveld method. Analysis of the known orthorhombic polar varieties of hilgardites, including the new compound, showed that their boron-oxygen frameworks are occupied by the Pb2+, Ca2+, Eu2+, and Ba2+ cations; the Cl−, Br−, and OH− anions; and water molecules in combinations determined by their sizes.

Crystal structure of the cubic modification of Cu2FeSnS4

AbstractThe structure of Cu2 − xFe1 − xSnS4, the last member of the isomorphous series Cu3FeS4-Cu2FeSnS4, was synthesized for the first time and solved by the Rietveld method (the WYRIET 3.3 version). The compound occurs as a cubic phase (a0 = 5.4179(5) Å) crystallizing in the sp. gr.

Crystal structure of the low-temperature modification of α-RbB3O5

P\bar 43m

Dehydration-induced structural transformations of the microporous zirconosilicate elpidite

. One-half of the tetrahedral cavities in the close packing of sulfur atoms [4e (xxx), x = 0.2583(5)] are statistically filled with metal atoms (Sn + Fe) and (Cu + Fe + Sn) [1a(0 0 0) and 3c (0 1/2 1/2), respectively]. The results of X-ray study (Rp = 2.33, Rwp = 3.00, s = 1.20, D = 1.53, RB = 2.52, and RF = 2.00) confirm the existence of the stannite “prototype” with a “small” cubic unit cell.

Crystal structure of the double magnesium zirconium orthophosphate at temperatures of 298 and 1023 K

Abstract The crystal structure of strontian potassicrichterite (Mg4.871Fe0.1263+Mn0.052)∑5.049 (Na1.425Ca0.348Sr0.297)∑2.07K0.873Si8.048O22(OH)2.15 - an unusual amphibole containing up to 3.7 wt.% SrO from the Murun alkaline massif, Eastern Siberia has been refined from X-ray powder diffraction data in monoclinic space group C2/m, with a = 10.0325(1) Å, b = 17.977(1) Å, c = 5.2698(1) Å, and β = 104.70(1)°. According to Mössbauer spectroscopy, nearly all iron occurs as Fe3+ in octahedral coordination. Rietveld refinement shows the Fe3+ to be ordered onto the M(2) site. Sr is completely ordered onto M(4).

Crystal structure of holtite I

The crystal structure of α-RbB3O5 was refined by the Rietveld method with due regard for anisotropic vibrations of rubidium atoms to Rp = 2.93, Rwp = 3.80, RB = 2.53, RF = 2.84, and s = 1.54. The compound is isostructural to CsB3O5: it is orthorhombic, sp. gr. P212121, a = 8.209(1), b = 10.092(1), c = 5.382(1) Å, and V = 445.9 Å 3. The framework structure is formed by the boron-oxygen [B2IIIBIVO5] − rings consisting of two [BO3]-triangles and a [BO4]-tetrahedron. The rings are linked to form systems of helical chains running along the twofold screw axes parallel 21 to the a-and b-axes and infinite channels parallel to the a-and c-axes, which accommodate Rb atoms. The data were collected on an ADP-2 diffractometer [CuKα radiation, Ni-filter, 12.00° < 2θ < 110.00°, a step in 2θ equal to 0.02°, count time 8 s per step, and 711 reflections α1 + α2)]. All the calculations were performed using version 3.3 of the WYRIET program. The comparison of the structures of α-and β-RbB3O5 and CsB3O5 revealed that the type of deformations in the framework structures of alkali-metal borates due to the changes of the temperature or the substitution of cations is determined by the role played by metal atoms, and especially, by large and heavy ions.

Synthesis and crystal structure of phosphates A2FeTi(PO4)3 (A = Na, Rb)

AbstractDouble cesium zirconium and barium zirconium orthophosphates with the compositions CsZr2(PO4)3 and Ba0.5Zr2(PO4)3, respectively, were prepared by thermal treatment of stoichiometric gels. The samples were characterized by electron-probe microanalysis and powder X-ray diffraction analysis. The crystal structures of both phosphates were refined by the Rietveld method within the space groups R