Alluaudite-Group Phosphate and Arsenate Minerals

ABSTRACT A systematic study of alluaudite, hagendorfite, and varulite was done using single-crystal X-ray diffraction, powder diffraction, and electron probe microanalysis of samples from 12 separate localities. The crystal structures of the representative alluaudite and hagendorfite samples were refined to R1 indices of 3.7 and 1.8%, respectively, using a Siemens P4 automated four-circle diffractometer equipped with a graphite monochromator and MoKα X-radiation. These samples and several others were analyzed with an electron microprobe to study variations in chemical composition. For the single-crystal analyses, the resulting unit formulae are (Na0.11□0.89)(Na0.59Mn0.27Ca0.14)Mn1.00(Fe3+1.64Al0.24Mg0.13)(PO4)3 for alluaudite, (Na0.79□0.21)(Na0.81Mn2+0.19)(Mn0.70Fe2+0.30)(Fe2+1.72Mg0.27Al0.01)(PO4)3 for hagendorfite, and (Na0.84□0.16)(Na0.71Ca0.23□0.06)Mn1.00(Fe3+0.89Fe2+0.68Mn0.42Mg0.01)(PO4)3 for varulite. Originally, a nomenclature scheme was proposed for the alluaudite-group minerals that was based on sequentially distributing the cations in the cell according to increasing polyhedron size, matching that size with increasing ionic radii of the cations. For alluaudite, the structural formula was written as X(2)4X(1)4M(1)4M(2)8(PO4)12, with the sites ordered in decreasing size of the discrete polyhedra. Later, the formula [A(2)A(2)'A(2)”2][A(1)A(1)'A(1)”2]M(1)M(2)2(PO4)3 was proposed, which takes into account the distinct crystallographic sites in the channels of the structure. More recently there has been a revision to the nomenclature of the group. The simplified structural formula for the alluaudite-type is now A(2)'A(1)M(1)M(2)2(TO4)3; the new nomenclature scheme has been adopted by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA-CNMNC), based on the contents of the M(1) and M(2) octahedral sites, and the results are reviewed here. Compounds belonging to the alluaudite structural family have been the focus of synthetic mineral studies for decades owing to the open-framework architecture and their unique physical properties. Improvements in synthesis methods have allowed researchers to substitute a wide range of elements into the alluaudite structure.

Tris(Para-Tolyl)Bismuth Bis(Bromodifluoroacetate). Synthesis and Structure Features

The interaction of tri(para-tolyl)bismuth with tert-butyl hydroperoxide and bromodifluoroacetic acid in diethyl ether have synthesized tris(para-tolyl)bismuth bis(bromodifluoroacetate). The X-ray diffraction pattern for the crystal has been obtained at 293 K on an automatic diffractometer D8 Quest Bruker (MoKα-radiation, λ = 0.71073 Å, graphite monochromator), the results are [C25H21O4F4Br2Bi, M 830.22, the triclinic syngony, the symmetry group P–1; cell parameters: a = 10.292(8), b = 11.752(9), c = 12.693(9) Å, α = 89.42(2) degrees, β = 78.04(3) degrees, γ = 78.04(3) degrees; V = 1424.8(18) Å3; the crystal size is 0.73×0.57×0.41 mm; intervals of reflection indexes are –13 ≤ h ≤ 13, –15 ≤ k ≤ 15, –16 ≤ l ≤ 16; total reflections 45443; independent reflections 7096; Rint 0.1030; GOOF 1.049; R1 = 0.0739, wR2 = 0.1834; residual electron density 2.11/–2.78 e/Å3], the bismuth atom have a distorted trigonal-bipyramidal coordination. The OBiO axial angle is 172.2(3) degrees; the sum of the CBiC angles in the equatorial plane is 360.6. The Bi–O and Bi–C bond lengths are 2.275(8), 2.295(8) Å and 2.187(10)–2.212(13) Å. The Bi•••O=С distances are 3.127(10) and 3.159(10) Å, which is less than the sum of the van der Waals radii of bismuth and oxygen (3.59 Å). There are no intermolecular contacts H∙∙∙Hal in the crystal. Complete tables of coordinates of atoms, bond lengths and valence angles for the structure are deposited at the Cambridge Structural Data Bank (no. 1923097; [email protected]; http: //www.ccdc.cam.ac.uk).

SYNTHESIS AND STRUCTURE OF TETRAPHENYLPHOSPHONIUM ARENESULFONATES

Interaction between pentaphenylphosphorus and arenesulfonic acids (mole ratio 1:1) in the benzene solution of tetraphenylphosphonium arenesulfonates has led to [Ph4P]+[O3SAr]−, Ar = Ph (I), C6H4Me-4 (II), C6H3(Me2-2,5) (III) (hydrate with 1.5 molecules of water). According to X-ray analysis, which was performed in the automatic four-circle Bruker D8 Quest diffractometer (Mo Kα-radiation, λ = 0.71073 Å, graphite monochromator), crystals I (C30H25O3PS, M 496.53 g/mol, crystal system moloclinic, space group P21/n, crystal size 0.25 × 0.2 × 0.15 mm), II(C31H27O3PS, M 510.56 g/mol, crystal system rhombic, space group Pna21, crystal size 0.48 × 0.18 × 0.12 mm) and III (C32H32O4.5PS, M 1097.16 g/mol, crystal system moloclinic, space group P2/c, crystal size 0.43 × 0.34 × 0.22 mm) include the tetrahedral cations (bond length equal 1.797(2)-1.799(2), 1.652(2)-1.999(3), 1.785(8)-1.815(7) Å; angles СРС equal 109.29(9)°-110.86(9)°, 104.04(13)°-115.14(12)°, 107.1(4)°-113.3(4)° in I, II and III respectively) and arenesulfonate anions (bond length equal S-O 1.4355(18)-1.4446(17), 1.313(3)-1.597(3), 1.431(6)-1.457(7) Å; angles ОSO 113.07(11)°-113.30(11)°, 107.5(2)°-117.2(2)°, 112.3(4)°-114.2(4)° in I, II and III respectively). In hydrate III the water molecules associate the cations and anions into the spatial grid through the intermolecular hydrogen bonds. The solvate [Ph4P]Br∙РhH (IV) has been obtained by the interaction of pentaphenylphosphorus with the hydrogen bromide. In IV the P-C bonds (1.7941(19)-1.803(2) Å) and angles СРС (107.93(9)°-112.96(9)°) are close to the similar values in the tetraphenylphosphonium arenesulfonates.

SYNTHESIS AND STRUCTURE OF POTASSIUM TETRAETHYLAMMONIUM HEXATHIOCYANATOPLATINATE(IV)

Potassium tetraethylammonium hexathiocyanatoplatinate(IV) (Et4N)(K)[Pt(SCN)6] (I) was synthesized by the reaction of potassium hexathiocyanatoplatinate(IV) with tetraethylammonium chloride in acetonitrile aqueous solution. Slow evaporation of the solvent led to the formation of large red-brown crystals. The product structure was determined by XRDA. The X-ray diffraction pattern of crystal I was carried out on a Bruker D8 QUEST diffractometer (MoKα radiation, λ = 0.71073 Å, graphite monochromator). [С14H20N7KPtS6, M = 712.92, Crystal system monoclinic, space group C 2/c, a = 10.432(8), b = 14.767(13), c = 16.300(13) Å, V = 2510(4) Å3, Z = 4, µ = 6.272 mm-1, F(000) = 1384, crystal size 0.86×0.66×0.50 mm]. The tetrahedral configuration of the tetraethylammonium cation is slightly distorted (CNC angles are 105.5(5)º-111.8(4)º, bond lengths N-С are 1.503(5)-1.519(5) Å). Platinum ions in anions have octahedral coordination (trans-angles SPtS are 180º, cis-angles SPtS are (88.47(4)º-91.53(4)º). The bond lengths Pt-S are equal to 2.373 (2)-2.37(2) Å. Potassium cations are coordinated by six nitrogen atoms of thiocyanate groups (distances N K (2.828(4)-2.896 (4) Å). Trans-angles NKN (128.44 (15)º-146.9 (2)º) are far from ideal values for the octahedron. Bridged thiocyanate ligands are bonded cations of the platinum and potassium. Ambidentate thiocyanate ligands are simultaneously coordinated to the K+ cation by nitrogen atoms. By means of the bridged thiocyanate ligands a three-dimensional coordination polymer is formed. The resulting structure is a three-dimensional grid, in the cells of which the cations of tetraethylammonium (Et4N)+ are located.

New, Experimental Powder Diffraction Data for Metastable Fe3B Phase Prepared According to ICDD Standards

In the present work X-ray studies were performed on annealed Fe78Nb2B20 amorphous alloy prepared by melt-spinning technique. All the samples were annealed in vacuum for 1 hour at temperatures up to 800°C. For the studied alloy -Fe and Fe2B are the stable, crystalline phases. The -Fe crystallized as the first crystalline phase in the sample annealed at 350°C. On the other hand, metastable Fe3B phase appeared to be stable during annealing in 425-800°C temperature range. The best fitting of the experimental X-ray data to as jet available ICDD files was obtained for Ni3P type structure (39-1315 – S.G.: I (82)). New, experimental powder diffraction data for metastable Fe3B phase prepared according to ICDD standards were elaborated for the sample annealed at 600°C. For this sample the best agreement between the calculated values of lattice constants and positions of experimental diffraction lines was obtained. The X-ray data were collected using X-Pert Philips diffractometer equipped with curved graphite monochromator on diffracted beam. The Treor program was applied for the analysis of X-ray diffraction data.

A comparison of a microfocus X-ray source and a conventional sealed tube for crystal structure determination

Experiments are described in which a direct comparison was made between a conventional 2 kW water-cooled sealed-tube X-ray source and a 30 W air-cooled microfocus source with focusing multilayer optics, using the same goniometer, detector, radiation (Mo Kα), crystals and software. The beam characteristics of the two sources were analyzed and the quality of the resulting data sets compared. The Incoatec Microfocus Source (IµS) gave a narrow approximately Gaussian-shaped primary beam profile, whereas the Bruker AXS sealed-tube source, equipped with a graphite monochromator and a monocapillary collimator, had a broader beam with an approximate intensity plateau. Both sources were mounted on the same Bruker D8 goniometer with a SMART APEX II CCD detector and Bruker Kryoflex low-temperature device. Switching between sources simply required changing the software zero setting of the 2θ circle and could be performed in a few minutes, so it was possible to use the same crystal for both sources without changing its temperature or orientation. A representative cross section of compounds (organic, organometallic and salt) with and without heavy atoms was investigated. For each compound, two data sets, one from a small and one from a large crystal, were collected using each source. In another experiment, the data quality was compared for crystals of the same compound that had been chosen so that they had dimensions similar to the width of the beam. The data were processed and the structures refined using standard Bruker andSHELXsoftware. The experiments show that the IµS gives superior data for small crystals whereas the diffracted intensities were comparable for the large crystals. Appropriate scaling is particularly important for the IµS data.

Development and application of laboratory X-ray fluorescence holography equipment

The X-ray fluorescence holography (XFH) method has drawn the attention of many researchers as a novel experimental technique for imaging a three-dimensional local atomic structure around a certain element in a single crystal. Synchrotron radiation (SR) has been mainly used for the measurements because of extremely weak signals that are about 0.3% of isotropic fluorescent radiation. The measurements limited to the use of a SR source clearly hinder from increasing the number of the users. Thus, we developed a laboratory XFH equipment with a conventional X-ray source by using a singly bent graphite monochromator with a large curvature and X-ray detector for a high counting rate. With this equipment, we have successfully demonstrated that high-quality hologram data of a gold single crystal almost equivalent to those with a SR source are obtained. Four different holograms are recorded in the normal and inverse XFH modes. An atomic image reconstructed from these holograms patterns shows a distinct atomic image of Au

Development of laboratory x-ray fluorescence holography equipment

Laboratory x-ray fluorescence holography equipment was developed. A single-bent graphite monochromator with a large curvature and a high-count-rate x-ray detection system were applied in this equipment. To evaluate the performance of this equipment, a hologram pattern of a gold single crystal was measured. It took two days, which was about one-third the time required for the previous measurements using the conventional x-ray source and several times that using the synchrotron source. The quality of the hologram pattern is as good as that obtained using the synchrotrons. Clear atomic images on (002) are reconstructed.