Olga V. Yakubovich

Refinement of the crystal structure of Na2Ti3O7

The crystals of Na2Ti3O7 were obtained by crystallization from flux. The structure of the compound was refined from X-ray diffraction data collected on a four-circle diffractometer (2θ/θ scanning technique, λMoKα radiation, graphite monochromator, θmax = 40°). The crystals are monoclinic a = 9.133(2) Å, b = 3.806(1) Å, c = 8.566(2) Å, β = 101.57(3)°, sp. gr. P21/m, Z = 2, ρcalcd = 3.435 g/cm3, R = 0.035, 1241 reflections with I ≥ 2σ(I). The geometric characteristics of the Ti-polyhedra are analyzed as to their positions in the trioctahedral ribbon. The polymorphism of the {Ti3O7}2− anionic radical in the structures of Na2Ti3O7 and PbTi3O7 is described. The topology and dimensionality of the { Ti3O7}2− anionic radical are demonstrated to depend on the type of the large cations located at the lattice points of the hexagonal close packing characteristic of both structures.

The mixed anionic framework in the structure of Na2{MnF[PO4]}

In the crystal structure of hydrothermally synthesized sodium manganese fluoride orthophosphate, Na2{MnF[PO4]}, two kind of cis-MnO4F2 octahedra share common vertices to form (Mn2F2O8) chains parallel to the b axis of the monoclinic unit cell. In the a and c directions these chains are linked by PO4 tetrahedra to form a three-dimensional framework of octahedra and tetrahedra. Na+ cations are located in the channels of this framework structure. The problem of {OTX5} mixed anionic radical polymorphism is discussed.

Crystal Structure of Chabazite K

AbstractThe crystal structure of the chabazite K with the formula (K1.33Na1.02Ca0.84)[Al4Si8O24] · 12.17H2O from late hydrothermalites in the Khibiny alkaline massif (Kola Peninsula) is established by X-ray diffraction analysis (CAD4 four-circle diffractometer, λMoKα radiation, graphite monochromator, T=193 K, 2θmax = 70°, R1 = 0.047 for 4745 reflections) on the basis of experimental data (6265 reflections) obtained from a twin (twinning parameter 0.535(1)): a = 13.831(3) Å, c = 15.023(5) Å, sp. gr.

Kyanoxalite, a new cancrinite-group mineral species with extraframework oxalate anion from the Lovozero alkaline pluton, Kola peninsula

R\bar 3m

Layer structure of (NH4)CoPO4

, Z = 3, ρcalcd = 2.016 g/cm3. It is shown that cations occupy five independent positions in large cavities of the tetrahedral Al,Si,O anionic framework in potassium-rich chabazite. A comparative crystallochemical analysis of chabazites of different composition and origin is performed.

The first vanadate-carbonate, K2Mn3(VO4)2(CO3): crystal structure and physical properties.

The crystal structure of the beryllium-rich cordierite [(Na0.28Ca0.19)(H2O)0.92](Mg1.86Fe0.1422−) · { Al3.39Be0.61Si5O18} was established by X-ray diffraction analysis (IPDS Stoe diffractometer, λMoKα radiation, graphite monochromator, 2θmax = 65°, R = 0.0186 for 1378 reflections): a = 16.850(3), b = 9.729(2), and c = 9.298(2) Å; V = 1524.3(4) Å3, sp. gr. Cccm, Z = 4, and ρcalcd = 2.655 g/cm3. The numbers of Mg and Fe atoms isomorphously occupying the octahedral positions, Al and Be atoms in tetrahedra, and Na and Ca atoms and H2O molecules in the framework cavities are refined. The hydrogen atom is localized and its coordinates and thermal displacement parameters are refined. Based on the comparative crystallochemical analysis of cordierites from different locations and origins, the regularities relating the unit-cell parameters b and c and the distortion index to the features of the chemical composition of the minerals under study are shown.

Crystal structure of britvinite [Pb7(OH)3F(BO3)2(CO3)][Mg4.5(OH)3(Si5O14)]: A new layered silicate with an original type of silicon-oxygen networks

Kyanoxalite, a new member of the cancrinite group, has been identified in hydrothermally altered hyperalkaline rocks and pegmatites of the Lovozero alkaline pluton, Kola Peninsula, Russia. It was found at Mount Karnasurt (holotype) in association with nepheline, aegirine, sodalite, nosean, albite, lomonosovite, murmanite, fluorapatite, loparite, and natrolite and at Mt. Alluaiv. Kyanoxalite is transparent, ranging in color from bright light blue, greenish light blue and grayish light blue to colorless. The new mineral is brittle, with a perfect cleavage parallel to (100). Mohs hardness is 5–5.5. The measured and calculated densitiesare 2.30(1) and 2.327 g/cm3, respectively. Kyanoxalite is uniaxial, negative, ω = 1.794(1), ɛ = 1.491(1). It is pleochroic from colorless along E to light blue along O. The IR spectrum indicates the presence of oxalate anions C2O42− and water molecules in the absence of CO32− Oxalate ions are confirmed by anion chromatography. The chemical composition (electron microprobe; water was determined by a modified Penfield method and carbon was determined by selective sorption from annealing products) is as follows, wt %: 19.70 Na2O, 1.92 K2O, 0.17 CaO, 27.41 Al2O3, 38.68 SiO2, 0.64 P2O5, 1.05 SO3, 3.23 C2O3, 8.42 H2O; the total is 101.18. The empirical formula (Z = 1) is (Na6.45K0.41Ca0.03)Σ6.89(Si6.53Al5.46O24)[(C2O4)0.455(SO4)0.13(PO4)0.09(OH)0.01]Σ0.68 · 4.74H2O. The idealized formula is Na7(Al5−6Si6−7O24)(C2O4)0.5−1 · 5H2O. Kyanoxalite is hexagonal, the space group is P63, a = 12.744(8), c = 5.213(6) -ray powder diffraction pattern are as follows, [d, [A] (I, %)(hkl)]: 6.39(44) (110), 4.73 (92) (101), 3.679 (72) (300), 3.264 (100) (211, 121), 2.760 (29) (400), 2.618 (36) (002), 2.216, (29) (302, 330). According to the X-ray single crystal study (R = 0.033), two independent C2O4 groups statistically occupy the sites on the axis 63. The new mineral is the first natural silicate with an additional organic anion and is the most hydrated member of the cancrinite group. Its name reflects the color (κɛανgoΣς is light blue in Greek) and the species-forming role of oxalate anions. The holotype is deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, registration no. 3735/1.

A new cubic form of caesium hexaaquamagnesium phosphate, Cs[Mg(H2O)6](PO4).

The crystal structure of the synthetic Ge-modification of the mineral natisite, Na2{ TiOGeO4}, has been refined by X-ray diffraction method (a four-circle diffractometer, 2θ/θ scanning, MoKα-radiation, θmax = 50°: a = 6.658(1), c = 5.161(1) Å, sp. gr. P4/nmm, Z = 2, ρcalcd = 3.58 g/cm3, R1 = 0.030, s = 1.131, wR(F2) = 0.058 (352 reflections with I≥2σI). The comparative crystallochemical analysis of the related (including hypothetical) phases with the anionic {MTO5} radicals (M = Ti, V, Ge; T = Ge, Si, P) is performed with the aim of revealing a possible relationship between the composition and the structure type of the compounds.