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Single crystals of Na2Cu+[Cu2+3O](AsO4)2Cl (1) and Cu3[Cu3O]2(PO4)4Cl2 (2) were prepared by chemical vapor transport reactions. Both crystal structures are based upon the same [O2Cu6]8+ chains formed by corner-sharing (OCu4)6+ tetrahedra and interconnected by (TO4)3− (T = P, As) tetrahedra into porous {[OCu3](TO4)2Cl}3− frameworks. The channels within the frameworks are occupied by Na+, Cu+ and Cl− ions in the crystal structure of 1, whereas the channels in the structure of 2 contain edge-sharing CuO4Cl tetragonal pyramids. Both compounds are structurally related to the previously described synthetic Na2Cu+[Cu2+3O](PO4)2Cl and NaCu2+[Cu2+3O](PO4)2Cl. The compound 2 is structurally and chemically related to yaroshevskite, Cu3[Cu3O]2(VO4)4Cl2, a mineral discovered in volcanic fumaroles, but the two structure types are drastically different. The crystal chemical analysis of the title and related compounds allows to recognize a family of at least four compounds based upon {[OCu3](TO4)2Cl}3− frameworks with channels occupied by different chemical constituents. [ABSTRACT FROM AUTHOR]

In the course of the investigation of the phase formation in a K-bearing uranyl sulfate system under low-temperature hydrothermal conditions, stepwise crystallization of eight chemically and structurally distinct uranyl-bearing phases, including six novel compounds, has been observed. The crystal structures of four new compounds are based on units with novel topologies, one of which has never been observed in uranyl sulfates and three others are unprecedented for the structural chemistry of inorganic oxysalts. The obtained phases were analyzed using single-crystal XRD, EDX, topological analysis and information-based structural complexity calculations. The analysis of the chemical evolution in the system shows that the amount of U and S in the crystalline phases increases and decreases, respectively, driven by the increase of the pH value. The solution was heated to 55 °C, which appears to be insufficient for the formation of zippeite-type K-bearing uranyl sulfates. The analysis of the behavior of structural complexity indicates that most complex compounds crystallize on the borders between stability fields of stable compounds with less complex structural architectures. [ABSTRACT FROM AUTHOR]

Experimental investigations of crystallization in a family of uranyl triacetate compounds with Na, K, Rb and Cs were performed. The crystal structures of two novel Cs- and Rb-bearing tri(acetato)uranylates were solved, and the content of H2O molecules in the crystal structure of K-bearing uranyl triacetate was refined. Synthesized compounds were analyzed using IR spectroscopy and single-crystal X-ray diffraction. Crystal chemical analysis of the M[(UO2)(CH3COO)3](H2O)n family (M = Na, K, Rb, Cs; n = 0–1.0) reveals the sequence of structural transformations depending on the size of alkali cation resulting in the symmetry reduction from cubic P 213 (for Na), through tetragonal I 41/a (for K and Rb) to triclinic P 1̅ space groups (for Cs), which is in accordance with the principle of morphotropism, suggested by Paul von Groth, founder of the Zeitschrift für Krystallographie journal, in 1870. [ABSTRACT FROM AUTHOR]

Single crystals of four novel uranyl selenate and selenite-selenate oxysalts with protonated ethylamine molecules, (C 2 H 8 N) 2 [(UO 2 )(SeO 4 ) 2 (H 2 O)](H 2 O) ( I ), (C 2 H 8 N) 3 [(UO 2 )(SeO 4 ) 2 (HSeO 4 )] ( II ), (C 2 H 8 N)[(UO 2 )(SeO 4 )(HSeO 3 )] ( III ), and (C 2 H 8 N)(H 3 O)[(UO 2 )(SeO 4 ) 2 (H 2 O)] ( IV ) have been prepared by isothermal evaporation from aqueous solutions. Uranyl-containing 1D and 2D units have been investigated using topological approach and information-based complexity measurements that demonstrate the evolution of structural units and the increase of topological complexity with the decrease of H 2 O content. [ABSTRACT FROM AUTHOR]

Chlormagaluminite is the only Cl-dominated hydrotalcite-supergroup mineral species with M2+:M3+ = 2:1. The holotype sample of chlormagaluminite from the Kapaevskaya volcanic pipe (Irkutsk Oblast, Siberia, Russia) has been chemically and structurally characterized. The average chemical composition of the mineral is (electron microprobe, OH content is calculated by stoichiometry and H2O from the crystal-structure data, wt. %): MgO 33.85, FeO 1.09, Al2O3 22.07, Cl 14.72, H2Otot 30.96, Cl=O −3.39, total 99.30. The empirical formula based on Mg + Al + Fe = 6 atoms per formula unit (apfu) is [Mg3.91Fe2+0.07Al2.02(OH)12]Cl2.02(H2O)2.0(2). The crystal structure has been solved from single-crystal X-ray diffraction data in the space group P63/mcm, a = 5.268(3), c = 15.297(8) Å and V = 367.6(4) Å3. The refinement converged to R1 = 0.083 on the basis of 152 unique reflections with I > 2σ(I) collected at room conditions. The powder pattern contains standard reflections of a 2H polytype and two additional reflections [(010), d010 = 4.574 Å; (110), d110 = 2.647 Å] indicative of Mg and Al ordering according to the 3 × 3 superstructure. The structure is based upon brucite-type octahedral layers with an ordered distribution of Mg and Al over octahedral sites. The Cl− anions and H2O molecules reside in the interlayer, providing a three-dimensional integrity of the structure. [ABSTRACT FROM AUTHOR]

The crystal structure of magnesian halotrichite has been refined for two samples collected as white efflorescences from the surface of geothermal fields associated with the Koshelevsky (sample VK4-09) and Centralny Semyachik (sample SC2-20) volcanoes (both Kamchatka peninsula, Russia). Halotrichite and its Mg-rich varieties are common products of the acid leaching of rocks, both volcanic and technogenic. The crystal structures of two halotrichite crystals were refined in the P21/n space group (vs. P21/c used previously) with the unit-cell parameters a = 6.1947(2)/6.1963(5) Å, b = 24.2966(8)/24.2821(14) Å, c = 21.0593(8)/21.063(2) Å, β = 96.512(4)/96.563(9) º, V = 3149.2(2)/3148.3(5) Å3, Z = 4 to R1 = 0.055 and 0.067 for 5673 and 3936 reflections with I > 2σI reflections, respectively. The crystal structure consists of isolated Al(H2O)6 octahedra, SO4 tetrahedra, H2O molecules and [X(SO4)(H2O)5]0 clusters (X = Fe, Mg). The chemical analyses of both samples show their enrichment of Mg at the Fe2+ site. The analysis of geometrical parameters of the crystal structures of halotrichite and its Mg-analogue pickeringite suggests that the localization of O atoms carried out in this work is more accurate and the single-crystal X-ray diffraction data for the first time allowed localization of hydrogen atom positions. The refined number of H2O molecules agrees with the ideal chemical formula. The crystal structure complexity of halotrichite is estimated as IG, total = 2305 bits/cell, which belongs to the family of very complex mineral structures. The contribution of hydrogen bonding system plays a significant role in the overall bonding scheme and the overall complexity of the crystal structure, increasing the Shannon information amount more than twice from IG, total(noH) = 988 bits/cell (no hydrogen atoms) to IG, total = 2305 bits/cell (all atoms including hydrogen). The comparative distribution of halotrichite relative to other Fe-Al hydrated sulfates from the standpoint of structural complexity is considered. [ABSTRACT FROM AUTHOR]

We report the crystal structures of four synthetic members of the variscite group (space group type Pbca) and of bonacinaite, the first naturally occurring scandium arsenate member of the metavariscite group. All structures were determined using single-crystal X-ray intensity data. The following members were all synthesised under either mild hydrothermal conditions or by wet-chemical methods (<90°C). CrAsO4⋅2H2O (deep green): a = 8.894(2), b = 9.946(2), c = 10.206(2) Å and V = 902.8(3) Å3; R1 = 2.14%. Tl3+PO4⋅2H2O (colourless): a = 10.2848(7), b = 8.8578(6), c = 10.3637(7) Å and V = 944.14(11) Å3 (data at –173°C); R1 = 2.56%. MnSeO4⋅2H2O (pale pink): a = 10.441(2), b = 9.2410(18), c = 10.552(2) Å and V = 1018.1(3) Å3; R1 = 2.19%. A different method of preparation of MnSeO4⋅2H2O yielded crystals with very similar unit-cell parameters, a = 10.4353(5), b = 9.2420(5) and c = 10.5349(6) Å; R1 = 2.25%. CdSeO4⋅2H2O (colourless) has a = 10.481(1), b = 9.416(1), c = 10.755(1) Å and V = 1061.4(2) Å3; R1 = 1.53%. The thermal behaviour of the two selenate members was studied by a combination of DSC and TG, supplemented by PXRD. Bonacinaite (IMA2018-056), metavariscite-type natural (Sc,Al)(As,P)O4⋅2H2O (ideally ScAsO4⋅2H2O), crystallises in the space group P21/n, with a = 5.533(1), b = 10.409(2), c = 9.036(2) Å, β = 91.94(3)° and V = 520.11(18) Å3; R1 = 3.66%. The structural formula, supported by chemical analysis, is (Sc0.807(1)Al0.193)(As0.767(7)P0.233)O4⋅2H2O. All structures are based on frameworks built by corner-sharing of TO4 tetrahedra (T = P5+, As5+ or Se6+) with MO4(H2O)2 (M = Mn2+, Cd2+, Cr3+, Sc3+ or Tl3+) octahedra. The flexible frameworks are reinforced by partly bifurcated, strong to weak hydrogen bonds. The crystal chemistry of all known synthetic and natural members of the variscite and metavariscite groups is discussed and compared, and the relative stabilities are evaluated. With the aid of the COMPSTRU program (Bilbao Crystallographic Server), a quantitative comparison of the crystal structures in both groups is given. Calculations of the structural and topological complexity reveal that the metavariscite structure type is structurally and topologically simpler than that of variscite. It is suggested that metavariscite and phosphosiderite are metastable kinetically stabilised phases, in contrast to thermodynamically stable variscite and strengite, respectively. The 3D frameworks of the members of both groups have been shown to be potential electrode materials for rechargeable Li ion batteries. [ABSTRACT FROM AUTHOR]