Crystal structure of Pb-exchanged form of zorite

The crystal structure of a Pb-exchanged form of zorite is studied by X-ray diffraction: Pb_3.95(Ca_0.1Sr_0.05)[Ti(Ti_0.80Nb_0.20)₄Si₁₂O₃₈(OH)] · 9.52H₂O (sp. gr. Cmmm, R = 0.0530 for 680 independent reflections). The structure retains the mixed polyhedral framework of zorite, Na₆[Ti(Ti,Nb)₄(Si₆O₁₇)₂(O,OH)₅] · 11H₂O. This framework is composed of xonotlite-like [Si₆O₁₇] ribbons linked to each other by columns of vertex-sharing (Ti,Nb)O₆ octahedra and isolated TiO₅ half-octahedra. Lead atoms in the Pb-exchanged form occupy one site, unlike Cs cations in the Cs-exchanged form of zorite, which are strongly disordered and partially occupy eight positions. The position of Pb²⁺ cations corresponds to the Na(2) position in the zorite structure, the Sr position in the Sr-exchanged form of ETS-4, and the K position in the K-exchanged form and is similar to the position of the water molecule W(3) in the structure of the Cs-exchanged form of zorite.     

Crystal chemistry of elpidite from Khan Bogdo (Mongolia) and its K- and Rb-exchanged forms

Elpidite Na₂ZrSi₆O₁₅ · 3H₂O [space group Pbcm, a = 7.1312(12), b = 14.6853(12), and c = 14.6349(15) Å] from Khan Bogdo (Mongolia) and its K- and Rb-exchanged forms K_1.78Na_0.16H_0.06ZrSi₆O₁₅ · 0.85H₂O [Cmce, a = 14.054(3), b = 14.308(3), and c = 14.553(3) Å] and Na_1.58Rb_0.2H_0.22ZrSi₆O₁₅ · 2.69H₂O [Pbcm, a = 7.1280(10), b = 14.644(3), and c = 14.642(3) Å] that were obtained by cation exchange at 90°C, as well as K_1.84Na_0.11H_0.05ZrSi₆O₁₅ · 0.91H₂O [Cmce, a = 14.037(3), b = 14.226(3), and c = 14.552(3) Å] and Rb_1.78Na_0.06H_0.16ZrSi₆O₁₅ · 0.90H₂O [Cmce, a = 14.2999(12), b = 14.4408(15), and c = 14.7690(12) Å], obtained at 150°C are studied by single-crystal X-ray diffraction and IR spectroscopy. The base of the structures is a heteropolyhedral Zr-Si-O framework whose cavities accommodate Na (K, Rb) cations and H₂O molecules.     

Ordering of cations in the voids of the anionic framework of the crystal structure of catapleiite

The pseudohexagonal crystal structure of the mineral catapleiite Na_1.5Ca_0.2[ZrSi₃(O,OH)₉] · 2(H₂O,F) from the Zhil’naya Valley in the central part of the Khibiny alkaline massif (Kola Peninsula, Russia) is studied by X-ray diffraction (XCalibur-S diffractometer, R = 0.0346): a = 20.100(4), b = 25.673(5), and c = 14.822(3) Å; space group Fdd2, Z = 32, and ρ_calcd = 2.76 g/cm³. Fluorine atoms substituting part of H₂O molecules in open channels of the crystal structure have been found for the first time in the catapleiite composition by microprobe analysis. The pattern of distribution of Na and Ca atoms over the voids of the mixed anionic framework consisting of Zr-octahedra and three-membered rings of Si-tetrahedra accounts for the pronounced pseudoperiodicity along the a and c axes of the pseudohexagonal unit cell and for the lowering of crystal symmetry to the orthorhombic one. It is shown that part of the hydrogen atoms of water molecules is statistically disordered; their distribution correlates with the pattern of the population of large eight-vertex polyhedra by Na and Ca atoms.     

Crystal structure of cation-deficient calciohilairite and possible mechanisms of decationization in mixed-framework minerals

The crystal structure of cation-deficient calciohilairite from the Lovozero massif (the Kola Peninsula) was established (Siemens P4 diffractometer, MoK _α radiation, 409 independent reflections with | F| > 4σ(F), anisotropic refinement, R(F) = 0.037). Like other representatives of the hilairite structure type, calcio-hilairite is described by the space group R32 (a = 10.498(2) Å, c = 7.975(2) Å, Z = 3), whereas its unit-cell parameter c is reduced by a factor of two. Two positions in the cavities of the mixed zirconium-silicon-oxygen framework are occupied by Ca and Na cations in the ratio of 1: 1 (partly occupied A(1) position) and oxonium cations (H₃O) ⁺ and H₂O molecules in the ratio of 1: 2 (A(2) position). Different types of isomorphous replacement accompanying the formation of cation-deficient mixed-framework structures (lovozerite, vinogradovite-lintisite, labuntsovite-nenadkevichite, eudialyte, etc.) are considered. Based on the X-ray diffraction data, the following scheme of isomorphism in the structure of cation-deficient calciohilairite is suggested: 2Na⁺ + H₂O ? 0.5Ca²⁺ + 1.5h□ + (H₃O)⁺, where □ is a vacancy.     

Synthesis and Crystal Structure of a New Mixed Alkali Oxalate A1?x(NH4)x(H2C2O4)(HC2O4)(H2O)2 with A?=?K, Rb

Abstract  

In the present study we report the synthesis, crystal structure, spectroscopic and thermal analysis of mixed alkali A_1−x (NH₄) _x (H₂C₂O₄)(HC₂O₄)(H₂O)₂ with A = K, Rb. Single crystal refinements showed that the two compounds Rb_0.86(NH₄)_0.14(H₂C₂O₄)(HC₂O₄)(H₂O)₂ and K_0.53(NH₄)_0.47(H₂C₂O₄)(HC₂O₄)(H₂O)₂ adopt P − 1 space group. The nine fold coordination cationic sites are randomly occupied by Rb⁺/NH₄ ⁺ and K⁺/NH₄ ⁺ respectively for rubidium and potassium compounds. The structure consists of a three-dimensional network formed by the succession along (c) axis of corrugated sheets formed by alkali polyhedra layers in the packing of four-membered rings [A₄(HC₂O₄)₂(H₂C₂O₄)₂] linked and bridged by oxalate groups that behave as bi and tetradentate ligand under three different coordination modes. The stability of the crystal lattice is ensured by interesting hydrogen bonding contacts: N–H···O and O–H···O. The thermal behavior under air reveals two anomalies at 368 and 402 K attributed respectively to a structural phase transition probably due to the reorientation of ammonium tetrahedral and to the release of crystalline water. IR spectroscopy further confirms that this material loses crystallization water gradually in the temperature range 400–460 K.     

Crystal structures of two new low-symmetry calcium-deficient analogs of eudialyte

The crystal structures of two new low-symmetry (sp. gr. R3) representatives of the eudialyte group from Mont Saint-Hilaire (Quebec, Canada) and the Lovozero massif (Kola Peninsula, Russia) were studied by single-crystal X-ray diffraction analysis and refined to R = 0.068 and 0.054 using 2899 reflections with F > 5σ(F) and 2927 reflections with F > 3σ(F), respectively. The idealized formulas of these representatives are Na₁₃(Ca₃Mn₃)Zr₃(Fe, Mn)₃(□)(Si)[Si₃O₉]₂[Si₉O₂₇]₂(O, OH, Cl)₃ · 2H₂O and Na₁₅(Ca₃Mn₃)Zr₃(Fe, Zr)₃(Si)(Si) · [Si₃O₉]₂[Si₉O₂₇]₂O₂(OH, F, Cl)₂ · 2H₂O. Both minerals are analogs of oneillite and are characterized by a low Ca content. The distinguishing features of the mineral from Quebec are that the M(4) site is essentially vacant (>50%) and Ca atoms occupy one independent site in the six-membered ring, whereas another site is occupied by Mn along with a small impurity of Na. In the mineral from the Lovozero massif, both the M(3) and M(4) sites are occupied predominantly by silicon, while Ca atoms are distributed between both octahedral sites of the six-membered ring, one of these sites being occupied predominantly by Mn.     

Synthesis and X-ray diffraction study of complex neptunium(VI) potassium chromate K2[(NpO2)2(CrO4)3(H2O)] · 3H2O

The crystal structure of the K₂[(NpO₂)₂(CrO₄)₃(H₂O)] · 3H₂O compound was established. The structure consists of anionic layers [(NpO₂)₂(CrO₄)₃(H₂O)] _n ²ⁿ , between which K+ ions and crystallization water molecules are located. The coordination polyhedra of Np atoms are distorted pentagonal bipyramids. All chromate ions are bound in a tridentate-bridging fashion. __________ Translated from Kristallografiya, Vol. 49, No. 4, 2004, pp. 676–680. Original Russian Text Copyright ? 2004 by Grigor’ev, Fedoseev, Budantseva, Bessonov, Krupa.     

Hydrothermal crystallization in the KF-ZrO2-SiO2-H2O system at 40°C: Phase equilibria and modeling of ZrSiO4, K2ZrSi6O15, K2ZrSi3O9, K3ZrF7, and ZrO2 crystal structures

The phase equilibria in the KF-ZrO₂ (nanocrystals)-SiO₂-H₂O system are studied for the ZrO₂: SiO₂ molar ratio ranging from 2: 1 to 1: 6 and the KF concentration C _KF ranging from 3 to 36 wt % under 0.1 GPa at 40°C. We established crystallization of three silicates—ZrSiO₄ (zircon), K₂ZrSi₆O₁₅ (deleite), K₂ZrSi₃O₉ (wadeite)—and K₃ZrF₇ fluoride and ZrO₂ and SiO₂ oxides. The structures of K-and Zr-based silicates obtained can be represented as an open framework formed by M octahedra (ZrO₆) that share vertices with T tetrahedra (SiO₄). With the increase of KF concentration, silicates “substitute” each other in the following sequence: ZrSiO₄ ?K₂ZrSi₆O₁₅ ? K₂ZrSi₃ O₉. Depending on the ZrO₂: SiO₂ ratio and C _KF concentration, K₃ZrF₇ fluoride is formed simultaneously with K₂ZrSi₃O₉ and K₂ZrSi₃O₉ + K₂ZrSi₆O₁₅. The characteristic features of formation of Zr-containing phases are discussed in the framework of the model of the matrix assembly of crystal structures from subpolyhedral structural units—clusters of cyclic type. The features of the phase formation in the system are compared with the characteristics determined earlier for the KOH-ZrO₂ (nanocrystals)-SiO₂-H₂O system at 40°C.     

Preparation and studies of new crystals in the K3H(SO4)2-(NH4)3H(SO4)2-H2O system

To elucidate the effect of isomorphic substitution on the kinetics of phase transitions, single crystals of (K _x (NH₄)_1?x ) _m H _n (SO₄)_{(m + n)/2} · yH₂O solid solutions are grown from the K₃H(SO₄)₂-(NH₄)₃H(SO₄)₂-H₂O system, whose end members are known to undergo superprotonic phase transitions of fundamentally different kinetics. The chemical composition of the single crystals grown is determined by energy dispersive X-ray microanalysis. The thermal and optical behavior of (K,NH₄)₉H₇(SO₄)₈ · H₂O single crystals is studied in the temperature range 295–420 K and the crystal structure at 295 K is determined. A comparison of the results of the studies with data for crystal K₉H₇(SO₄)₈ · H₂O published earlier shows that the substitution of ammonium for potassium atoms lowers the temperature of the structural phase transition by 8 K.     

Crystal structure of octapotassium octasulfatodiceriate pentahydrate

Single crystals without Co and Ni have been crystallized by the substitution method in the K₂Ni(SO₄)₂-Ce(SO₄)₂-H₂SO₄-H₂O system using K₂Co(SO₄)₂ · 6H₂O, K₂ (Co,Ni)(SO₄)₂ · 6H₂O, or K₂Ni(SO₄)₂ · 6H₂O as protocrystals. The structure of the single crystals obtained has been established by X-ray diffraction analysis. The crystal structure contains dimer complex anions [Ce₂(μ-SO₄)₂(SO₄)₆]⁸⁻, K⁺ cations, and crystallization water molecules.     

(C2N2H10)2Mg(HP2O7)2·2H2O synthesis and crystal structure

(C₂N₂H₁₀)₂Mg(HP₂O₇)₂·2H₂O, is a new inorganic organic hybrid structure. It has been synthetized using wet chemistry. Its crystal structure consists of cis- and trans-edge sharing [MgO₄(H₂O)₂] octahedra resulting in chains, which are linked via [HP₂O₇] units to form [Mg(HP₂O₇)₂(H₂O)₂]⁴⁻ layers. The Mg²⁺ cations and the ethylendiammonium cations are located on centers of inversion. The ethylendiammonium cations are alternately located in the interlayer space. The cohesion of the crystal is well ensured by coulombic interactions between anions and cations and by several hydrogen bonds. The diphosphate anion shows an eclipsed conformation.     

New Data on Isomorphism in Eudialyte-Group Minerals. I. Crystal Structure of Titanium-Rich Eudialyte from the Kovdor Alkaline Massif

An abnormally titanium-rich mineral of the eudialyte group was studied by IR spectroscopy and X-ray diffraction. The trigonal unit cell parameters are a = 14.165(1) Å, c = 30.600(5) Å, V = 5317.23(4) ų, sp. gr. R3m. The crystal structure was refined to R = 0.034 with anisotropic displacement parameters using 2530 reflections with F > 3σ(F). The idealized formula of the mineral (Z = 3) is Na₈(H₃O)₅(K,Ce,Sr)₂Ca₆Zr₂Ti_1.2(Fe,Mn)_0.6Si₂₆O₇₂(OH)₂Cl · 4H₂O. At the ratio Zr: Ti ~ 2: 1, titanium atoms lie in four sites and are not predominant in any of them. Another distinguishing feature of the mineral is the structural separation of chemical elements, such that K, Sr, and Ce cations and H₃O groups are randomly distributed between four split sites to form polyhedra with different volumes. The isomorphism of Zr and Ti in eudialyte-group minerals is discussed.     

Synthesis and Structure of a Novel Polyoxomolybdate Lanthanide Complex: [Er2(H2O)14Cr(OH)6Mo6O18][Cr(OH)6Mo6O18]?·?14H2O

Abstract  A novel polyoxometalate compound consisting of Anderson-type anions and trivalent lanthanide cations, [Er₂(H₂O)₁₄Cr(OH)₆Mo₆O₁₈][Cr(OH)₆Mo₆O₁₈]·14H₂O (1), has been synthesized in aqueous solution and characterized by single crystal X-ray diffraction, elemental analyses, IR spectrum and TG analyses. Single crystal X-ray diffraction reveals that compound 1 crystallizes in the triclinic space group P-1 with a = 11.046 (5) ?, b = 11.653 (5) ?, c = 13.935 (5) ?, α = 75.006 (5)°, β = 84.497(5)°, γ = 89.515(5)°. The bulk ions of compound 1 in the cell unit exhibit orthorhombic C-centered packing mode, the eight [Cr(2)(OH)₆Mo₆O₁₈]³⁻ anions occupy the eight corners and the two [Er₂(H₂O)₁₄Cr(OH)₆Mo₆O₁₈]³⁺ cations occupy the centres of two opposite faces, whereas anions and cations are linked together via hydrogen bonding interactions tightly forming a three-dimensional supramolecular architecture, which contains one-dimensional channels occupied by free water molecules. Index Abstract  The bulk ions of compound 1 in the cell unit exhibit orthorhombic C-centered packing mode, the eight [Cr(2)(OH)₆Mo₆O₁₈]³⁻ anions occupy the eight corners and the two [Er₂(H₂O)₁₄Cr(OH)₆Mo₆O₁₈]³⁺ cations occupy the centres of two opposite faces, whereas anions and cations are linked together via hydrogen bonding interactions tightly forming a three-dimensional supramolecular architecture, which contains one-dimensional channels occupied by free water molecules. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Crystal structure of a new ten-layer feldspathoid of the cancrinite group

A new cancrinite-group mineral with composition (Na,Ca)₂₄K₁₀[(Si,Al)₆₀O₁₂₀](SO₄)_5.6Cl_1.5(CO₃)_0.4·11H₂O from the Sacrofano Caldera (Italy) was studied by X-ray diffraction. The unit-cell parameters are a = 12.847 Å, c = 26.461 Å, sp. gr. P3; the R factor is 5.7% based on 3111 reflections with F > 5σ(F). The mineral has a ten-layer stacking sequence of six-membered rings ACACBCBCBCAC…, whereas franzinite (Na,K)₃₀Ca₁₀[Si₃₀Al₃₀O₁₂₀](SO₄)₁₀·2H₂O having the same unit cell (sp. gr. P321) is characterized by a stacking sequence ABCABACABCAB. Both minerals contain three types of cages, including the cancrinite cage. The distinguishing feature of the analog of franzinite is that it contains the largest cages (liottite and giuseppettite) instead of the sodalite and bystrite (losod) cages found in the franzinite structure.     

Dilatometric and ultrasound study of [NH<Subscript>2</Subscript>(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>]MnCl<Subscript>3</Subscript> · 2H<Subscript>2</Subscript>O crystals

The unit-cell parameters of [NH₂(CH₃)₂]MnCl₃ · 2H₂O crystals are determined by X-ray diffraction analysis and the velocities of longitudinal ultrasonic waves in these crystals are measured by the echo-pulse method in the temperature range 100–315 K. The coefficients of thermal expansion along the principal crystallographic axes are derived from the temperature dependences of the unit-cell parameters. The temperature dependences of the characteristics studied reveal kink anomalies at temperatures of ～125, 179, 203, 260, and 303 K. These anomalies are indicative of structural transformations in the [NH₂(CH₃)₂]MnCl₃ · 2H₂O crystals, which may be related to the dynamics of dimethylammonium cations.     

Temperature-induced changes in the single-crystal structure of K9H7(SO4)8 · H2O

Interest in superprotonic crystals of M _m H _n (XO₄)_{(m + n)/2} is associated with the solution to the fundamental problem of modern condensed matter physics: investigations of structural phase transitions and the stabilization of phases with high proton conductivity with the aim of designing new functional materials. The available data suggest that changes in the physical properties in these crystals can occur through different structural mechanisms. To reveal the structural conditionality for anomalies in the physical properties, the crystals of K₉H₇(SO₄)₈ · H₂O were studied by X-ray diffraction in the temperature range of 25–463 K, and the crystal structure of the high-temperature phase was determined at 418 K (sp. gr. Pcan). The results of the study indicate that the occurrence of high conductivity in K₉H₇(SO₄)₈ · H₂O crystals at high temperatures is associated with the diffusion of water of crystallization, the hydrogen-bond network rearrangement, and the motion of K ions. The hydrogen-bond rearrangement and the hindered back diffusion of water to the crystal stabilize the high-temperature phase and ensure its supercooling to low temperatures.     

Structural characteristics of Na,Fe-decationated eudialyte with the symmetry <Emphasis Type="Italic">R</Emphasis>3

The crystal structure of a new highly decationated representative of the eudialyte group has been established (R = 0.055, 1734 |F|). The mineral is described by the simplified formula (H₃O)₉Na₂(K, Ba,Sr)₂Ca₆Zr₃[Si₂₆O₆₆(OH)₆](OH)₃Cl · H₂O (Z = 3). The unit-cell parameters are a = 14.078(3) Å, c = 31.24(1) Å; V = 5362 ų; sp. gr. R3. Being chemically and structurally related to the hydrated analogues studied previously (in particular, to potassium oxonium eudialyte), the new mineral differs from its analogues in that it has a higher degree of Na-and Fe-cation depletion. The replacement of 3/4 of Na cations by loose and mobile H₃O groups results in structure destabilization, which is seen from the high values of the thermal parameters of the atoms and the loss of the symmetry plane.     

Computer simulation of the self-assembly of crystal structures of zeolites Ca64(Sr,K,Ba)48(Cu12(O,Cl))4[Si192Al192O786](H2O) n (tschoertnerite, TSC, V = 31 614 Å3) and Ca2K2[Al6Si6O24](H2O)10 (willhendersonite, cha, V = 804 Å3) from template nanocluster precursors K48 and K12

The self-assembly of zeolites Ca₆₄(Sr,K,Ba)₄₈(Cu₁₂(O,Cl))₄[Si₁₉₂Al₁₉₂ O₇₈₆](H₂O) _n (tschoertnerite, TSC-type framework, V = 31614 ų) and Ca₂K₂[Al₆Si₆O₂₄] (H₂O)₁₀ (willhendersonite, CHA-type framework, V = 804 ų), which form paragenetic associations, has been simulated using computational methods (TOPOS program package). A new method for analyzing zeolites of any complexity has been used, which is based on the complete expansion of the three-dimensional structural graph (3D factor graph) in tiles and the selection of nonintersecting tiles forming a packing. The code of self-assembly of 3D structures from complementary linked nanocluster precursors is reconstructed: primary chain → microlayer → microframework. A supracluster precursor K48 with the symmetry $\bar 4$ 3m, formed of four K12 clusters corresponding to the t-hpr tile, is established for TSC. The K48 cluster contains Ca template cations, which stabilize its local region in the stages of K12 → K24 → K48 self-assembly. Bifurcations of evolution paths (structural branching points) during the self-assembly of TSC and CHA microframeworks are established in the stage of formation of the K24 supracluster from invariant templated K12 clusters. The models under consideration explain the 100% localization of B = Ca cations, which play the role of templates, and the 50% occupation of the positions of K, Sr, and Ba spacer cations (in TSC) and K spacer cations (in CHA).     

Hydrate Stabilization in the Three-Dimensional Hydrogen-Bonded Structure of the Brucinium Compound,Bis(2,3-dimethoxy-10-oxostrychnidinium) Biphenyl-4,4′-disulfonate Hexahydrate

Abstract  

The crystal structure of the 2:1 proton-transfer compound of brucine with biphenyl-4,4 ′ -disulfonate, bis(2,3-dimethoxy-10-oxostrychnidinium) biphenyl-4,4 ′ -disulfonate hexahydrate (1) has been determined at 173 K. Crystals are monoclinic, space group P2₁ with Z = 2 in a cell with a = 8.0314(2), b = 29.3062(9), c = 12.2625(3) ?, β = 101.331(2)°. The crystallographic asymmetric unit comprises two brucinium cations, a biphenyl-4,4 ′ -disulfonate dianion and six water molecules of solvation. The brucinium cations form a variant of the common undulating and overlapping head-to-tail sheet sub-structure. The sulfonate dianions are also linked head-to-tail by hydrogen bonds into parallel zig-zag chains through clusters of six water molecules of which five are inter-associated, featuring conjoint cyclic eight-membered hydrogen-bonded rings [graph sets R ₃³(8) and R ₄³(8)], comprising four of the water molecules and closed by sulfonate O acceptors. These chain structures occupy the cavities between the brucinium cation sheets and are linked to them peripherally through both brucine N⁺–H···O_sulfonate and O_carbonyl···H–O_water to sulfonate O bridging hydrogen bonds, forming an overall three-dimensional framework structure. This structure determination confirms the importance of water in the stabilization of certain brucine compounds which have inherent crystal instability.     

Crystal structure of chabazite K

The crystal structure of the chabazite K with the formula (K_1.33Na_1.02Ca_0.84)[Al₄Si₈O₂₄] · 12.17H₂O from late hydrothermalites in the Khibiny alkaline massif (Kola Peninsula) is established by X-ray diffraction analysis (CAD4 four-circle diffractometer, λMoK_α radiation, graphite monochromator, T=193 K, 2θ_max = 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. \(R\bar 3m\), Z = 3, ρ_calcd = 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.