Synthesis and crystal structure of new phosphate NaFe 4 2+ Fe 3 3+ [PO4]6

New sodium iron orthophosphate NaFe ₄ ²⁺ Fe ₃ ³⁺ [PO₄]₆ was synthesized by the hydrothermal method. The crystal structure (sp. gr. $P\bar 1$ ) was established by the heavy-atom method, with the exact chemical formula of the compound being unknown; R _hkl = 0.0492, R _whkl = 0.0544, S = 0.52. The new compound is analogous to iron phosphate Fe ₃ ²⁺ Fe ₄ ³⁺ [PO₄]₆ studied earlier. However, these two compounds differ in the Fe²⁺ and Fe³⁺ contents, because Na⁺ ions in the new compound are located at the centers of symmetry not occupied earlier.     

Crystal chemistry of Li,GeVI-germanates: Combinatorial-topological analysis and modeling of crystal structures

The combinatorial-topological analysis of the structures of framework Li,Ge-germanates of the compositions Li₂Ge^VIGe ₂ ^IV O₆(OH)₂ (sp. gr. B ₂/b), Li₂Ge^VIGe ₃ ^IV O₉ (sp. gr.Pcca), Li₄Ge ₂ ^VI Ge ₇ ^VI O₂₀ (sp. gr. C2), and Li₂Ge^VIGe ₆ ^IV O₁₅ (sp. gr. Pbcn) has been made with the separation of subpolyhedral structural units (SPSUs) built by octahedra and tetrahedra. The topologically invariant SPSUs are separated in three-dimensional frameworks of the structures. A possible mechanism of the matrix assemblage from the SPSU invariants in crystal structures of the framework Li,Ge-germanates is suggested.     

X-Ray diffraction and IR-spectroscopic studies of UO2(n-C3H7COO)2(H2O)2 and Mg(H2O)6[UO2(n-C3H7COO)3]2

Single crystals of UO₂(n-C₃H₇COO)₂(H₂O)₂ (I) and Mg(H₂O)₆[UO₂(n-C₃H₇COO)₃]₂ (II) are synthesized. Their IR-spectroscopic and X-ray diffraction studies are performed. Crystals I are monoclinic, a = 9.8124(7) Å, b = 19.2394(14) Å, c = 12.9251(11) Å, β = 122.423(1)°, space group P2₁/c, Z = 6, and R = 0.0268. Crystals II are cubic, a = 15.6935(6) Å, space group $Pa\bar 3$ , Z = 4, and R = 0.0173. The main structural units of I and II are [UO₂(C₃H₇COO)₂(H₂O)₂] molecules and [UO₂(C₃H₇COO)₃]^? anionic complexes, respectively, which belong to AB ₂ ⁰¹ M ₂ ¹ (I) and AB ₃ ⁰¹ (II) crystal chemical groups of uranyl complexes (A = UO ₂ ²⁺ , B ⁰¹ = C₃H₇COO^?, and M ¹ = H₂O). A crystal chemical analysis of UO₂ L ₂ · nH₂O compounds, where L is a carboxylate ion, is performed.     

Crystal structure and IR spectroscopic study of (CN3H6)2[(UO2)2(C2O4)(CH3COO)4]

Compound (CN₃H₆)₂[(UO₂)₂(C₂O₄)(CH₃COO)₄] is synthesized and characterized by IR spectroscopy and single-crystal X-ray diffraction [a = 8.5264(2) Å, b = 13.8438(4) Å, c = 10.7284(2) Å, β = 103.543(1)°, space group P2₁/n, Z = 2, and R = 0.0258]. The main structural units of the crystals are binuclear [(UO₂)₂C₂O₄(CH₃COO)₄]^2? groups, which belong to the A ₂ K ⁰² B ₄ ⁰¹ crystal chemical group of uranyl complexes (A = UO ₂ ²⁺ , K ⁰² = C₂O ₄ ^2? , and B ⁰¹ = CH₃COO^?). The coordination polyhedron of the uranium atom is the UO₈ hexagonal bipyramid with the oxygen atoms of the uranyl ion at the axial positions. Uranium-containing groups and guanidinium cations are connected by electrostatic interactions and by the hydrogen bond system, which involves hydrogen atoms of guanidinium cations and oxygen atoms of oxalate and acetate anions. The results of the spectroscopic study of the compound agree with the X-ray diffraction data.     

Hole defects in the crystal structure of synthetic lipscombite (Fe 4.7 3+ Fe 2.3 2+ )[PO4]4O2.7(OH)1.3 and genetic crystal chemistry of minerals of the lipscombite-barbosalite series

The crystal structure of a synthetic analog of the mineral lipscombite (Fe _2.3 ²⁺ Fe _4.7 ³⁺ )[PO₄]₄O_2.7(OH)_1.3 obtained under hydrothermal conditions in the LiF-Fe₂O₃-(NH₄)₂HPO₄-H₂O system is resolved (R = 0.040) by X-ray diffraction analysis (Bruker Smart diffractometer with a highly sensitive CCD detector, MoK _α radiation): a = 14.776(3) Å, b = 14.959(3) Å, c = 7.394(1) Å, β = 119.188(4)°, sp. gr. C2/c, Z = 4, ρ_exp = 3.8 g/cm³, ρ_calcd = 3.9 g/cm³. Fe²⁺ and Fe³⁺ cations are statistically distributed in each of four crystallographically independent positions, while occupying the corresponding octahedra with probabilities of 60, 90, 100, and 91%. The ratio Fe²⁺/Fe³⁺ in the composition of the crystals was established by Mössbauer spectroscopy. Lipscombite is interpreted as a mineral of variable composition described by the formula (Fe _x ²⁺ Fe _n?x ³⁺ )[PO₄]₄O_y(OH)_4?y . The field of stability is determined as a function of the iron content and the ratio Fe²⁺/Fe³⁺. It is shown that at n = 6 iron cations are ordered in octahedra and barbosalite structure is formed. An interpretation of genetically and structurally related members of the lipscombite family within a unified polysomatic series is proposed.     

Bimetallic hydrogen sulfates K4 M II[H(SO4)2]2(H2O)2 (M II = Mn or Zn)

Hydrogen sulfate hydrates K₄{M ^II[H(SO₄)₂]₂(H₂O)₂}, where M ^II = Mn or Zn, are synthesized, and their single-crystal structures are determined by X-ray diffraction. The structural units of the orthorhombic crystals (space group Pccn) are potassium and M ^II cations, SO ₄ ^2? and HSO ₄ ^? anions, and water molecules. Strong (2.52 Å) and moderate-in-strength (2.71–2.75 Å) hydrogen bonds link the anions and water molecules into hexamers. The M ^II cations, which have the octahedral environment (Mn-O, 2.14–2.19 Å and Zn-O, 2.07–2.11 Å), link the hexamers into flat layers. The structures of bimetallic hydrogen chalcogenate hydrates with different compositions are compared.     

Crystal structure of new synthetic Ca,Na,Li-carbonate-borate

In the process of studying the phase formation in the Li₂CO₃-CaO-B₂O₃-NaCl system, new Ca,Na, Li-carbonate-borate has been synthesized under hydrothermal conditions. The crystal structure of carbonate-borate with the crystallochemical formula Ca₄(Ca_0.7Na_0.3)₃(Na_0.7□ _0.3)Li₅[B ₁₂ ^t B ₁₀ ^Δ O₃₆(O,OH)₆](CO₃)(OH) · (OH,H₂O) was refined to R _hkl = 0.0716 by the least squares method in the isotropic approximation of atomic thermal vibrations without the preliminary knowledge of the chemical composition and the formula (sp. gr. R3, a _rh = 13.05(2) Å, α = 40.32(7)]°, V = 838(2) ų, a _h = 8.99(2), c _h = 35.91(2) Å, V = 2513(2) ų, Z = 3, d _calcd = 2.62 g/cm³, Syntex P $\bar 1$ diffractometer, 3459 reflections, 2θ-θ method, λMo). The structure has a new boron-oxygen radical [B ₁₂ ^t B ₁₀ ^Δ O₃₆(O,OH)₆] _∞∞ ^15? , a double layer of nine-membered [B ₆ ^t B ₃ ^Δ O₁₅(O,OH)₃]^7.5?-rings bound by BO₃-triangles, and twelve-membered [B ₆ ^t B ₆ ^Δ O_19.5(O,OH)₃]^7.5? rings. This allows one to relate this compound to megaborates with complex boron-oxygen radicals. The structure is built from two types of blocks consisting of Ca,Na,B-and Li,B-polyhedra alternating along the c-axis, which explains the perfect cleavage of the crystals along the (0001) plane.     

Synthesis and crystal structures of bimetallic hydrogen sulfates M I M II [H(SO4)2](H2O)2 (M I = K, Cs; M II = Zn, Mn) and selenate KMg[H(SeO4)2](H2O)2

Single crystals of acid salt hydrates M ^I{M ^II[H(XO₄)₂](H₂O)₂}, where M ^I, M ^II, and X are K, Zn, and S (I); K, Mn, and S (II); Cs, Mn, and S (III); or K, Mn, and Se (IV), respectively, were synthesized and studied by X-ray diffraction analysis. Compounds I–IV (space group $P\bar 1$ ) are isostructural to each other and to hydrate KMg[H(SO₄)₂](H₂O)₂ (V) studied earlier. Structures I–V, especially, the M ^I-O, M ^II-O, and X-O distances and the O?H?O (2.44–2.48 Å) and O_w-H?O (2.70–2.81 Å) hydrogen bonds, are discussed.     

The absorption and circular dichroism spectra of langasite family crystals doped with chromium ions

The absorption and circular dichroism spectra of langasite family crystals, La₃Ga₅SiO₁₄, La₃Ga₅GeO₁₄, Ca₃Ga₂Ge₄O₁₄, Sr₃Ga₂Ge₄O₁₄ (red), Sr₃Ga₂Ge₄O₁₄ (green), La₃Ta_0.5Ga_5.5O₁₄, and La₃Nb_0.5Ga_5.5O₁₄, which were doped with chromium ions, have been investigated in the range of 240–850 nm. It is shown that chromium ions are incorporated into the structure of the investigated crystals both in the octahedrally (Cr³⁺ ion in 1a octahedron) and tetrahedrally (Cr⁴⁺ ion in 2d tetrahedron) coordinated positions. The ion ratio Cr³⁺/Cr⁴⁺ changes in a wide range in the crystals studied.     

Crystal structures of cesium and dimethylammonium cupradecaborates, Cs[CuB10H10] and (CH3)2 NH2[CuB10H10]

The crystal structures of Cs[CuB₁₀H₁₀] (I) and (CH₃)₂NH₂[CuB₁₀H₁₀] (II) are studied (R = 0.0398 and 0.0510 for 1225 and 2728 observed reflections in I and II, respectively). Crystals I and II are built of [(CuB₁₀H₁₀)^?]∞ anionic chains and cations. The distorted tetrahedral coordination of the Cu⁺ ions is formed by four pairs of B-H atoms from two polyhedral anions. The Cu-B bond lengths in I and II are 2.159–2.287(6) and 2.130–2.285(9) Å, respectively. The coordination of the Cu⁺ ions in II includes only edges between apical and equatorial vertices of the anions. In I, both the edges of the apical belt and those between two equatorial vertices are involved in coordination. The ability of the B₁₀H ₁₀ ^2? anion to coordinate metals by the equatorial edge is established for the first time.     

Nuclear57Fe relaxation in Fe2+-containing NiFe2O4 and CoFe2O4 single crystals

Spin-lattice (T ₁) and spin-spin (T ₂) relaxation times of ⁵⁷Fe nuclei in the single-crystal NiFe₂O₄ and CoFe₂O₄ ferrites containing Fe²⁺ ions have been studied in the temperature range of 4.2–100 K by a spin-echo technique. The peaks of relaxation rates T ₁ ^?1 and T ₂ ^?1 caused by the presence of Fe²⁺ ions were observed for both ferrites in the ranges 38–42 and 28–32 K, respectively. The analysis of the results obtained with invocation of the data on ferromagnetic resonance and the measurements of the temperature dependence of resistivity shows that the mechanism of nuclear relaxation responsible for “impurity” peaks and is a slow relaxation process caused by electron exchange Fe²⁺ ? Fe³⁺, characterized by a low activation energy.     

Synthesis, properties, and crystal structure of barium 1-oxyethylidenediphosphonatohydroxogermanate(IV) polyhydrate Ba3[Ge(μ-OH)(μ-Oedph)]6 · 25H2O

The barium salt of 1-oxyethylidenediphosphonatohydroxogermanium acid Ba₃[Ge(μ-OH)(μ-Oedph)]₆ · 25H₂O (I) (H₄Oedph is 1-oxyethylidenediphosphonic acid) was synthesized and studied by X-ray diffraction. The complex was characterized by elemental analysis, thermogravimetry, and IR spectroscopy. The hexanuclear cyclic complex anions [Ge(μ-OH)(μ-Oedph)] ₆ ^6-t- ] cations, and water molecules of crystallization are the structural units of the crystal of I.     

Influence of rare-earth impurities on the Ge and Ga local structure in the Ca3Ga2Ge3O12 glass

The present contribution presents X-ray absorption fine structure (XAFS) measurements and analysis of the Ge and Ga local structure in glass of Ca₃Ga₂Ge₃O₁₂ composition, doped with rare-earth metals (Ce, Eu, Ho, Er in the amount of 0.7 wt% and Nd in the amount of 1.0 wt%). The Ge and Ga ion neighborhoods in the considered glass samples have been compared with data obtained for undoped glass. The results have shown that introduction of rare-earth ions modifies the local structure around the Ga ions in the glass network, leaving the same occurrence ratio of the GaO₄ and GaO₆ structural units as in undoped Ca₃Ga₂Ge₃O₁₂ glass. At the same time, the GeO₂ subsystem remains completely unaffected by the presence of rare-earth dopants.     

Derivation of the conditions for equivalent positions in crystals: The dissymmetrization of barite by electron spin resonance spectra

The conditions for equivalent positions on the (hkl) face of growing crystal are derived using symmetry elements of the space group. It is shown by the example of the sp. gr. D _2h ¹⁶ that the conditions of equivalent position formation coincide with conditions of the reflection of diffracted beams by crystal. It is established that electron spin resonance (ESR) centers in barite, SO ₄ ^? (I) and SO ₄ ^? (II), with only two conjugate spectra with equal intensity out of four, and SO ₄ ^? (III), with a different intensity of conjugate spectra K _??M = 2, are localized into the growth pyramid of the (001) face with a [010] step. SO ₂ ^? , SO ₃ ^? ,, and SO ₄ ^? (IV) centers, having an identical intensity of the conjugate ESR spectra with K _??M = 2, are localized into the growth pyramid of the (210) face with a growth step [001].     

Mixed tetrahedral anionic framework in the K3Ga2(PO4)3 crystal structure

The crystal structure of a new synthetic potassium gallophosphate K₃Ga₂(PO₄)₃ grown from a solution in the melt of a mixture of GaPO₄ and K₂MoO₄ is determined using X-ray diffraction (Bruker Smart diffractometer, 2θ_max= 56.6°, R = 0.044 for 2931 reflections, T = 100 K). The main crystal data are as follows: a = 8.661(2) Å, b = 17.002(4) Å, c = 8.386(2) Å, space group Pna2₁, Z= 4, and ρ_calcd = 2.91 g/cm³. The synthesized crystals represent the third phase in the structure type previously established for the K₃Al₂[(As,P)O₄]₃ compound. It is shown that the structure consists of a three-dimensional anionic microporous tetrahedral framework of the mixed type, which is formed by PO₄ and GaO₄ tetrahedra shared by vertices. Large-sized cations K⁺ occupy channels of the zeolite-like framework. The crystal chemical features of the formation of structure types of compounds with mixed frameworks described by the general formula A ₃ ⁺ M ₂ ³⁺ (TO₄)₃ (where A = K, Rb, (NH₄), Tl; M = Al, Ga, Fe, Sc, Yb; T = P, As) are analyzed.     

Cation distribution in the structure of titanium-containing ludwigite

The crystal structure of natural titanium-containing ludwigite has been refined. The unit-cell parameters are a = 9.260 ± 0.002 Å, b = 12.294± 0.002 Å, c = 3.0236± 0.0005 Å, sp. gr. Pbam, and R = 0.0288. The observed cation distribution over the M1-M4 positions corresponds to the structural formula (Mg_0.5)(Mg_1.0)(Mg_0.338Fe _0.162 ²⁺ )(Fe _0.47 ³⁺ Ti _0.21 ⁴⁺ Mg _0.15 ²⁺ Al _0.10 ³⁺ Fe _0.07 ²⁺ (BO₃)O₂. Highly charged titanium ions in the M4 position are balanced mainly with magnesium and not with divalent iron ions.     

Oxygen-conducting compounds with La2Mo2O9 structure in the ternary system La2Mo2O9-Sm2W2O9-Sm2Mo2O 9 + : Synthesis and properties

Polycrystalline samples in the ternary system La₂Mo₂O₉-Sm₂W₂O₉-Sm₂Mo₂O ₉ ⁺ were synthesized in air. The region of the existence of compounds with the lanthanum molybdate (La₂Mo₂O₉) structure in this system was determined. The polymorphism of the synthesized compounds was studied. Doping with samarium or with samarium and tungsten was shown to lead to the suppression of the transition between the monoclinic and cubic phases α → β and the appearance of the transition β _ms → β between two cubic phases. In samples with a high samarium content, the phase transition β _ms → β manifests itself as significant anomalies in the temperature dependences of the dielectric permeability and electric conductivity. An increase in the concentration of samarium in the samples leads to a substantial decrease in the conductivity compared with the nondoped compound La₂Mo₂O₉.     

New oxygen-and lead-deficient lead borate Pb 0.9 (I) Pb 0.6 (II) [BO2.25]2 = 2Pb0.75[BO2.25] and its relation to aragonite and calcite structures

Anhydrous oxygen-and lead-deficient lead borate of the composition Pb _0.9 ^(I) Pb _0.6 ^(II) [BO_2.25]₂ = 2Pb_0.75[BO_2.25] (sp. gr. P312) has been obtained by the hydrothermal synthesis. New acentric borate possesses optical nonlinearity comparable with the optical nonlinearity of α-quartz. The crystal structure of new borate is determined and refined by two X-ray diffraction methods—the single crystal diffractometry and the full-profile analysis. All the positions in the structure, except for those of the boron atom in the triangular coordination, are occupied only partly; one of the two lead positions is split. It is established that new borate is closely related to calcium carbonates—aragonite, calcite, and paralstonite. With an increase of the temperature, new borate undergoes the reversible phase transition into the centrosymmetric, most probably, aragonite-like phase.     

Strain of interatomic bonds and crystallochemical aspects of AB 1 2/′ B 1 2/″ O3 oxides with perovskite structure

A method for determining the strain characteristics of interatomic bonds in crystals of ternary oxides AB ₁ ^2/′ B ₁ ^2/″ O₃ with perovskite structure, i.e., AB ₁ ^2/′ B ₁ ^2/″ O₃ (B″ = Nb, Ta, Sb, Re, or Bi) and AB ₁ ^2/′2+ B ₁ ^2/″6+ O₃ (B″ = Mo, W, Re, Os, or U), is developed. A linear relationship is established between the effective lengths of unstrained B-O bonds (l _0BO) and the lengths of unstrained B′-O (l _0B′O) and B″-O (l _0B″O) bonds, which differs from the Vegard rule. The found values of l _0B″O for ternary oxides with perovskite structure turned out to be close to the average interatomic B″-O distances in crystals of polymorphic phases of low-symmetry simple oxides. It is shown that the average length of the unstrained Pb-O bond in PbB ₁ ^2/′ B ₁ ^2/″ O₃ perovskites corresponds to the length of the same bond in binary oxides PbBO₃. For ternary oxides with perovskite structure, a linear correlation between the bond-strain energy and the temperature of their transition to the cubic phase is established. A linear correlation is found between the ratios of the Curie temperatures and the bond-strain energy for lead niobates and tantalates.     

Insertion of ethyl isothiocyanate into tungsten hexachloride: Crystal structure of ethyl-(4-ethyl-5-thioxo[1.2.4]dithiazolidin-3-ylidene)ammonium oxopentachlorotungstate(VI)

A product of the insertion of two isothiocyanate molecules into the same W-Cl bond, namely, W-Cl-WCl₅{N(Et)C(S)N(Et)C(S)Cl} (I), is synthesized by the reaction of WCl₆ with EtNCS in a dichloroethane solution. The hydrolysis of compound I results in the formation of single crystals of the complex . The structure of crystals II is determined using X-ray diffraction. It is demonstrated that structural units of crystals II are the [W^VIOCl₅]^? anionic complexes and the ethyl-(4-ethyl-5-thioxo[1.2.4]dithiazolidin-3-ylidene)ammonium cations.