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Single crystals of Rb2CaCu6(PO4)4O2 were synthesized by a hydrothermal method in the multicomponent system CuCl2–Ca(OH)2–RbCl–B2O3–Rb3PO4. The synthesis was carried out in the temperature range from 690 to 700 K and at the general pressure of 480–500 atm [1 atm = 101.325 kPa] from the mixture in the molar ratio 2CuO:CaO:Rb2O:B2O3:P2O5. The crystals studied by single‐crystal X‐ray analysis were found to be monoclinic, space group C2, a = 16.8913 (4), b = 5.6406 (1), c = 8.3591 (3) Å, β = 93.919 (3)°, V = 794.57 (4) Å3. The crystal structure of Rb2CaCu6(PO4)4O2 is similar to that of shchurovskyite and dmisokolovite and is based upon a heteropolyhedral open framework formed by polar layers of copper polyhedra linked via isolated PO4 tetrahedra. The presence of well‐isolated 2D heteropolyhedral layers in the title compound suggests low‐dimensional magnetic behavior which is masked, however, by the fierce competition between multiple ferromagnetic and antiferromagnetic exchange interactions. At TC = 25 K, Rb2CaCu6(PO4)4O2 reaches a magnetically ordered state with large residual magnetization. [ABSTRACT FROM AUTHOR]

Ca9−xMgxEu(PO4)7 solid solution with a β-Ca3(PO4)2-type (β-TCP) structure was obtained using a solid-state technique and studied by X-ray diffraction, and luminescence and dielectric spectroscopy. The luminescent properties were measured, and the optical properties were related to the structural properties of the material. The number of bands for the 5D0 → 7F0 transition in the emission spectra depended on the cationic composition. Detailed investigation of the 5D0 → 7F0 transition of Eu3+ in the host lattice revealed changes in the number of Shtark components and, thus, europium-occupied sites in the structure. This data, in conjunction with the dielectric loss tangent (tan δ), indicate the appearance of the center of symmetry with increasing magnesium concentration up to 1. The analysis of different approaches allowed the establishment of three compositional areas in Ca9−xMgxEu(PO4)7 solid solution: 0 ≤ x ≤ 0.5 (R3c, ferroelectric phase), 0.5 < x < 0.8 (R3c + R3¯c), and 0.8 ≤ x ≤ 1.0 (R3¯c, antiferroelectric phase). The X-ray diffraction method does not allow these phases to be distinguished. It was found that magnesium cations have a significant effect on the luminescent properties of Ca9−xMgxEu(PO4)7 solid solution. The present research reveals that Eu3+ emission luminescence spectroscopy can be used as a method for the determination of the symmetry of crystalline phases that are very similar in structure. [ABSTRACT FROM AUTHOR]

Uranyl vanadate compounds with divalent cations, M(UO2)(V2O7) (M = Ca, Sr) and Sr3(UO2)(V2O7)2, were synthesized by flux crystal growth, and their crystal structures were solved using single‐crystal X‐ray diffraction data. Ca(UO2)V2O7 and Sr(UO2)V2O7 were synthesized from reactants with molar ratios M:U:V of 1:1:2 and identical heating conditions, and increasing the M:U:V ratio to 3:1:4 resulted in Sr3(UO2)(V2O7)2. Crystallographic data for M(UO2)V2O7 compounds are: a = 7.1774(18) Å, b = 6.7753(17) Å, c = 8.308(2) Å; V = 404.01(18) Å3; space group Pmn21, Z = 2 for Ca; a = 13.4816(11) Å, b = 7.3218(6) Å, c = 8.4886(7) Å; V = 837.91(12) Å3; space group Pnma, Z = 4 for Sr. Compound Sr3(UO2)(V2O7)2 has a = 6.891(3) Å, b = 7.171(3) Å, c = 14.696(6) Å, α = 85.201(4)˚, β = 78.003(4)˚, γ = 89.188(4)˚; V = 707.9(5) Å3; space group P1, Z = 2. The framework structure of Sr(UO2)(V2O7) is related to that of Pb(UO2)(V2O7) reported previously, while that of Ca(UO2)(V2O7) has a different topology. The topological polymorphism of the [(UO2)(V2O7)]‐type framework may be due to the differing ionic radii of the guest M2+ cations. Compound Sr3(UO2)(V2O7)2 has a modular structure based on two different types of electroneutral layers: [Sr(UO2)(V2O7)] and [Sr2(V2O7)]. Structural complexities were calculated, and Raman spectra were collected and their peaks were assigned. [ABSTRACT FROM AUTHOR]

Uranyl vanadate compounds with divalent cations, M(UO2)(V2O7) (M = Ca, Sr) and Sr3(UO2)(V2O7)2, were synthesized by flux crystal growth, and their crystal structures were solved using single‐crystal X‐ray diffraction data. Ca(UO2)V2O7 and Sr(UO2)V2O7 were synthesized from reactants with molar ratios M:U:V of 1:1:2 and identical heating conditions, and increasing the M:U:V ratio to 3:1:4 resulted in Sr3(UO2)(V2O7)2. Crystallographic data for M(UO2)V2O7 compounds are: a = 7.1774(18) Å, b = 6.7753(17) Å, c = 8.308(2) Å; V = 404.01(18) Å3; space group Pmn21, Z = 2 for Ca; a = 13.4816(11) Å, b = 7.3218(6) Å, c = 8.4886(7) Å; V = 837.91(12) Å3; space group Pnma, Z = 4 for Sr. Compound Sr3(UO2)(V2O7)2 has a = 6.891(3) Å, b = 7.171(3) Å, c = 14.696(6) Å, α = 85.201(4)˚, β = 78.003(4)˚, γ = 89.188(4)˚; V = 707.9(5) Å3; space group P1, Z = 2. The framework structure of Sr(UO2)(V2O7) is related to that of Pb(UO2)(V2O7) reported previously, while that of Ca(UO2)(V2O7) has a different topology. The topological polymorphism of the [(UO2)(V2O7)]‐type framework may be due to the differing ionic radii of the guest M2+ cations. Compound Sr3(UO2)(V2O7)2 has a modular structure based on two different types of electroneutral layers: [Sr(UO2)(V2O7)] and [Sr2(V2O7)]. Structural complexities were calculated, and Raman spectra were collected and their peaks were assigned. [ABSTRACT FROM AUTHOR]

Unusual agpaitic syenites containing up to 25 vol.% lamprophyllite-group minerals (lamprophyllite, fluorlamprophyllite, barytolamprophyllite, and the new mineral species fluorbarytolamprophyllite, IMA 2016–089) have been discovered in the Niva intrusion and Mokhnatye Roga alkaline dyke belonging to the Kola Alkaline Province, northwestern Russia. The other main components of the rocks are potassium feldspar, Ti-rich aegirine-augite, aenigmatite, alkaline amphiboles, astrophyllite, natrolite, and ferripyrophyllite. Three generations of lamprophyllite-group minerals can be distinguished based on their morphological features. The new mineral fluorbarytolamprophyllite is the F-dominant analogue of barytolamprophyllite and the Ba-dominant analogue of fluorlamprophyllite. It represents the early generation of lamprophyllite-group minerals (LGM) and forms brown prismatic crystals, their radial aggregates and marginal zones of fluorlamprophyllite crystals. The lustre of the new mineral is vitreous to pearly. Mohs hardness is 2.5. Dcalc is 3.662 g/cm3. The mineral is optically biaxial (+), α = 1.738(3), β = 1.745(4), γ = 1.777(4) (589 nm), 2 V (meas.) = 55(5)°, 2 V (calc.) = 51°. The chemical composition (electron microprobe, water determined by TGA, wt.%) is: Na2O 10.01, K2O 2.65, MgO 0.43, CaO 0.64, SrO 5.59, BaO 16.23, MnO 0.50, FeO 4.44, Al2O3 0.08, TiO2 27.31, ZrO2 0.22, Nb2O5 0.91, Ta2O5 0.15, SiO2 29.35, F 2.41, H2O 0.26, total 101.18. The empirical formula based on 18 anions is (Ba0.865Sr0.44K0.46Na0.26)Σ2.025(Na2.38Ca0.09Fe0.47Mn0.06)Σ3.00(Ti2.79Mg0.09Fe0.035Nb0.06Zr0.015Ta0.01)Σ3.00(Si3.99Al0.01)Σ4.00 O16[F1.04O0.72(OH)0.24]Σ2.00. The IR spectrum is given. The strongest lines of the powder X-ray diffraction pattern are [d, Å (I,%) (hkl)]: 9.692 (40) (200), 3.726 (59) (−311), 3.414 (67) (311), 3.230 (96) (300), 3.013 (53) (−5–11), 2.780 (100) (221), 2.662 (52) (002). The crystal structure has been solved and refined to R1 = 5.07 based on 2897 independent reflections with I > 2σ(I). Fluorbarytolamprophyllite is monoclinic, space group C2/m. The unit-cell parameters refined from the powder data are: a = 19.520(5), b = 7.0995(17), c = 5.3896(20) Å, β = 96.657(23)°; V = 741.86(24) Å3, Z = 2. At Niva and Mokhnatye Roga, most of the LGM were formed during magmatic stage of syenite crystallization from alkaline melt enriched in Na, K, Ba, Fe, Ti and F. Compositional variation of the examined LGM and their textural relations show changes in the Sr/Ba ratio in the parental melt and increasing activity of F and Ba in derivatives fluids as the main factors driving this variation. [ABSTRACT FROM AUTHOR]

A novel hydrated magnesium uranyl germanate, Mg[(UO2)2(Ge2O6(OH)2)]·(H2O)4.4, has been synthesized under hydrothermal conditions at 200 °C. The orthorhombic unit-cell parameters are a=10.829(6), b=7.625(4), c=16.888(10) Å, V=1394.5(1) Å3, space group Cmcm, Z=4. The crystal structure is based on β-U3O8-type sheets of corner- and edge-sharing U6+O7 pentagonal bipyramids. The GeO3(OH) tetrahedra and GeO4(OH) trigonal bipyramids are linked to form [Ge2φ8] diortho groups that fill the hexagonal-shaped windows within the sheets. The uranyl germanate layers are connected through Mgφ6 octahedra. The disorder of the [Ge2φ8] diortho groups leads to different local structure types with layered- and framework-like characters. A review of the crystal structures of uranyl minerals and actinide-bearing synthetic compounds based on β-U3O8 topological-type sheets is provided. Structural complexity parameters (IG,total=176.19 bits/unit cell) indicate that the title compound is one of the simplest actinyl compounds among this family. [ABSTRACT FROM AUTHOR]

Crystal structure, and thermal, dielectric and optical second-harmonic activities were investigated for whitlockite-type Ca8.6Pb1.9(VO4)7 (1), Ca7Pb3.5(VO4)7 (2) and Ca5.6Pb4.9(VO4)7 (3) single crystals. The refinement of the structure revealed splitting of the M3 and M4 sites into two and three sub-positions, respectively. Splitting of the M3 and M4 sites strongly enhances nonlinear optical activity, measured on powders, with the effect vanishing at ferroelectric phase transitions at elevated temperatures. Single crystals (1) and (2) undergo two structural transformations: ferroelectric one between 750–1150 K and a subsequent phase transition at higher temperatures. The structural mechanism of the ferroelectric phase transition is analyzed with respect to the rearrangement of Ca2+ and Pb2+ over their positions in the ferroelectric and paraelectric phases. Large Pb2+ ion substitution for calcium results in unit cell expansion with consequent extending of ion migration channels, thus leading to enhanced ionic conductivity in the Pb-rich materials. It is concluded that in spite of steric hindrances for lead cations, they effectively move between positions M2 → M4 → M1 or M1 → M4 → M2 together with calcium cations across the crystal. The cation conduction pathways as well as the migration energies of Ca2+ and Pb2+ cations were calculated by the bond valence energy landscape (BVEL) method. Among the obtained single crystals, (3) demonstrated the highest ionic conductivity, maximum second harmonic generation (SHS) signal and the lowest temperature of ferroelectric phase transition. [ABSTRACT FROM AUTHOR]

The new eudialyte-group mineral siudaite, ideally Na8(Mn2+2Na)Ca6Fe3+3Zr3NbSi25O74(OH)2Cl·5H2O, was discovered in a peralkaline pegmatite situated at the Eveslogchorr Mt., Khibiny alkaline massif, Kola Peninsula, Russia. The associated minerals are aegirine, albite, microcline, nepheline, astrophyllite, and loparite-(Ce). Siudaite forms yellow to brownish-yellow equant anhedral grains up to 1.5 cm across. Its lustre is vitreous, and the streak is white. Cleavage is none observed. The Mohs’ hardness is 4½. Density measured by hydrostatic weighing is 2.96(1) g/cm3. Density calculated using the empirical formula is equal to 2.973 g/cm3. Siudaite is nonpleochroic, optically uniaxial, negative, with ω = 1.635(1) and ε = 1.626(1) (λ = 589 nm). The IR spectrum is given. The chemical composition of siudaite is (wt%; electron microprobe, H2O determined by HCN analysis): Na2O 8.40, K2O 0.62, CaO 9.81, La2O3 1.03, Ce2O3 1.62, Pr2O3 0.21, Nd2O3 0.29, MnO 6.45, Fe2O3 4.51. TiO2 0.54, ZrO2 11.67, HfO2 0.29, Nb2O5 2.76, SiO2 47.20, Cl 0.54, H2O 3.5, -O = Cl − 0.12, total 99.32. According to Mössbauer spectroscopy data, all iron is trivalent. The empirical formula (based on 24.5 Si atoms pfu, in accordance with structural data) is [Na7.57(H2O)1.43]Σ9(Mn1.11Na0.88Ce0.31La0.20Nd0.05Pr0.04K0.41)Σ3(H2O)1.8(Ca5.46Mn0.54)Σ6(Fe3+1.76Mn2+1.19)Σ2.95Nb0.65(Ti0.20Si0.50)Σ0.71(Zr2.95Hf0.04Ti0.01)Σ3Si24.00Cl0.47O70(OH)2Cl0.47·1.82H2O. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is trigonal, space group R3m, with a = 14.1885(26) Å, c = 29.831(7) Å, V = 5200.8(23) Å3 and Z = 3. Siudaite is chemically related to georgbarsanovite and is its analogue with Fe3+-dominant M2 site. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 6.38 (60) (-114), 4.29 (55) (-225), 3.389 (47) (131), 3.191 (63) (-228). 2.963 (100) (4-15), 2.843 (99) (-444), 2.577 (49) (3-39). Siudaite is named after the Polish mineralogist and geochemist Rafał Siuda (b. 1975). [ABSTRACT FROM AUTHOR]

Single crystals of Ca9Y(VO4)7 (1), Ca9Y(VO4)7:Li+ (2) and Ca9Y(VO4)7:Mg2+ (3) were grown by the Czochralski method. Their chemical composition was analyzed by ICP spectroscopy and their crystal structure was examined by single crystal X-ray analysis. The crystals are characterized by trigonal symmetry, space group R3c. Hexagonal unit-cell parameters are as follows: a=10.8552(1) Å, c=38.0373(2) Å, V=3881.65(1) Å3 for 1; a=10.8570(1) Å, c=38.0161(3) Å, V=3880.77(4) Å3 for 2; a=10.8465(1) Å, c=38.0366(2) Å, V=3875.36(3) Å3 for 3. All crystals are characterized by β-Ca3(PO4)2-type structure with statistical distribution of Ca2+ and Y3+ over M1, M2 and M5 sites in different ratios and with completely empty M4-cationsite. The impurity of Mg2+cations in structure 2 has been detected in octahedral M5 site. Ferroelectric phase transitions are evidenced by DSC and SHG. At about 1220 and 1300 K, they demonstrate phase transitions. Upon heating the symmetry of the crystal structure changes according to the scheme R3c→R3̅c→R3̅m and is restored during consequent cooling. The first of them is of ferroelectric and the second of non-ferroelectric nature. Even a small amount of impurities in Ca9Y(VO4)7 structure is accompanied by a noticeable decrease in the temperature of the ferroelectric-paraelectric phase transition. [ABSTRACT FROM AUTHOR]

The first uranyl beryllophosphate, [(UO2)2{Be(H2O)2(PO4)2}]·(H2O), has been synthesized under hydrothermal conditions at 200°C. The monoclinic unit-cell parameters are: a=9.3361(1), b=8.8545(4), c=9.6592(10) Å, β=93.211(1)°, V=797.21(6) Å3, space group P2/n, Z=2. The crystal structure has been solved by direct methods and refined to final R1=4.92% using 1294 I>3σ(I) reflections in the anisotropic approximation. The structure consists of sheets of UrO5 pentagonal bipyramids and PO4 tetrahedra. UrO5 bipyramids are linked by edge-sharing to form infinite chains. Adjacent chains of UrO5 bipyramids are connected by sharing alternating edges of uranyl bipyramids with PO4 tetrahedra. The resulting sheets are based on the well-known uranophane anion-topology. Be atoms are tetrahedrally coordinated by two oxygen atoms of PO4 tetrahedra and two water molecules in the interlayer space. One isolated water molecule also occurs in the interlayer space, where it is held in position by H bonds. The connection between the phosphorus and beryllium tetrahedra leads to formation of an unbranched trimer [BeP2O8(H2O)2]4− observed for the first time in inorganic oxysalts. [ABSTRACT FROM AUTHOR]

Agardite-(Ce) from Clara Mine, Schwarzwald, Germany, has been investigated by means of electron microprobe analysis, single-crystal X-ray analysis, XANES spectroscopy and IR spectroscopy. Hexagonal unit-cell parameters are: a = 13.598(6), c = 5.954(3) Å; V = 953.5(2) Å3; space group P63/m. The structure has been solved and refined to final R1 = 3.87%, wR2 = 5.02 for 786 I > 3σ(I). Hydrogen atoms have been localized. The crystal-chemical formula is (Z = 2): A(1)(Ce0.82Ca0.14Sr0.04)Σ1.00A(2)(Ca0.03Ce0.02)Σ0.05 [Cu5.75(Fe3+, Mn)0.20]Σ5.95 [T(1)(AsO4)2.96T(2)(SbO4)0.04)]Σ3.00 (OH)5.96O0.04·3H2O. Hydrogen bonding in agardite-series minerals has been characterized for the first time. IR spectra of agardite-(Ce) and agardite-(Nd) from Lavrion used for comparison, as well as structural data indicate the presence of isolated H+ cations that do not form strong covalent bonds with coordinating O atoms. Agardite-(Ce) from Clara Mine forms epitaxial growths with the Sb-analogue of auriacusite. The latter mineral was characterized by EDS analyses; its typical empirical formulae are Ca0.06Ce0.04Fe3+1.06Cu0.89[(SbO4)0.58(AsO4)0.38(SiO4)0.04]Σ1.00(O,OH) and Ca0.075Ce0.04Fe3+0.93Cu0.97[(SbO4)0.59(AsO4)0.35(SiO4)0.06]Σ1.00(O,OH). The formation of uniaxial growths of the Sb-analogue of auriacusite and agardite-(Ce) is caused by the close values of their c parameters (for auriacusite s.s. c  =  5.9501(5) Å). Three-valence state of iron and five-valence of antimony in both minerals has been validated by means of Fe K- and Sb L2,3-edge XANES spectroscopy. [ABSTRACT FROM AUTHOR]

A hydroxyl-dominant analogue of gadolinite-(Y) (OH-Gad) has been discovered in the Heftetjern granitic pegmatite, southern Norway, in association with late-stage rare-earth-element containing minerals. The empirical formula, based on ten O atoms per formula unit, is (Y1.285Ca0.55Ce0.07La0.04Nd0.01)Σ1.955(Fe2+0.57□0.43)Be2.02Si1.995O8.48(OH)1.52. The mineral is monoclinic, space group P21/ c, a = 4.7514 (10), b = 7.5719 (16), c = 9.9414 (2) Å, β = 90.015 (4)°, V = 357.663 (3) Å3 and Z = 2. The density calculated using the empirical formula is 3.903 g cm−3. The crystal structure was refined to R = 0.0217 for 776 reflections with I > 2σ( I). OH-Gad is isostructural with gadolinite-(Y) and it is characterized by the predominance of OH− over O2− at the anionic Ø-site. The refined crystal-chemical formula is: A(Y1.25Ca0.55Ce0.2) X(Fe2+0.57□0.43) ZBe2 TSi2O8Ø[(OH)0.86O0.59(OH)*0.55] ( Z = 2). The possible orientation and local environment of the hydroxyl group were suggested based on bond-valence sum calculations and geometrical analysis of the crystal structure. The infrared spectrum confirms disordering of H atoms. OH-Gad seems to be a potentially new mineral, the first simultaneously hydroxyl- and iron-dominant member of the gadolinite subgroup. It is an OH-analogue of gadolinite-(Y) and an Fe2+-analogue of hingganite-(Y). [ABSTRACT FROM AUTHOR]

The crystal structure, thermal, dielectric and second harmonic generation (SHG), and nonlinear optical activity data for whitlockite-type Ca9Yb(VO4)7 single crystals were obtained on one and the same sample produced by means of the Czochralski method. The crystal structure refinement has revealed that Yb3+ cations substitute for Ca2+ ions only in the M1, M2 and M5 positions of the whitlockite-type structure. Dielectric, differential thermal analysis and SHG data have shown that Ca9Yb(VO4)7 belongs to the family of high-temperature Ca3(VO4)2 ferroelectrics with Curie temperature Tc = 1221 K, where the symmetry changes from R3c to R3̅c. At higher temperatures a previously unknown complementary phase transition is discovered at T2 = 1276 K and is associated with the symmetry change during heating from R3̅c to R3̅m. Unlike other whitlockites, two phase transitions in Ca9Yb(VO4)7 are separated by a broad interval (ΔT = 55 K) which allows one to register two phase transitions by DSC and dielectric measurements. According to the thermal type both transitions are classified as first-order transformations and their structural mechanisms are considered. Inhomogeneity in the cation distribution is argued to have a crucial influence on the optical quality and ferroelectric domain structures of Ca9Yb(VO4)7 and other whitlockite-type laser crystals. [ABSTRACT FROM AUTHOR]

Eleonorite, ideally Fe3+ 6 (PO4)4O(OH)4· 6H2O, the analogue of beraunite Fe2+Fe3+ 5 (PO4)4(OH)5·6H2O with Fe2+ completely substituted by Fe3+, has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification as a mineral species (IMA 2015-003). The mineral was first described on material from the Eleonore Iron mine, Dünsberg, near Giessen, Hesse, Germany, but during this study further samples were required and a neotype locality is the Rotläufchen mine, Waldgirmes, Wetzlar, Hesse, Germany, where eleonorite is associated with goethite, rockbridgeite, dufrénite, kidwellite, variscite, matulaite, planerite, cacoxenite, strengite and wavellite. Usually eleonorite occurs as red-brown prismatic crystals up to 0.2 mm × 0.5 mm × 3.5 mm in size and in random or radial aggregates up to 5 mm across encrusting cavities in massive 'limonite'. The mineral is brittle. Its Mohs hardness is 3. Dmeas = 2.92(1), Dcalc = 2.931 g cm-3. The IR spectrum is given. Eleonorite is optically biaxial (+), α = 1.765(4), β = 1.780(5), γ = 1.812(6), 2Vmeas = 75(10)°, 2Vcalc = 70°. The chemical composition (electron microprobe data, H2O analysed by chromatography of products of ignition at 1200°C, wt.%) is: Al2O3 1.03, Mn2O3 0.82, Fe2O3 51.34, P2O5 31.06, H2O 16.4, total 99.58. All iron was determined as being trivalent from a Mössbauer analysis. The empirical formula (based on 27 O apfu) is (Fe3+ 5:76Al0.18Mn3+ 0:09)Σ6.03(PO4)3.92O(OH)4.34·5.98H2O. The crystal structure (R = 0.0633) is similar to that of beraunite and is based on a heteropolyhedral framework formed by M(1-4)Ø6-octahedra (where M= Fe3+; Ø=O2-, OH- or H2O) and isolated PO4 tetrahedra, with a wide channel occupied by H2O molecules. Eleonorite is monoclinic, space group C2/c, a = 20.679(10), b = 5.148(2), c = 19.223(9) Å, β = 93.574(9)°, V = 2042.5(16) Å3 and Z = 4. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I,%) (hkl)] are 10.41 (100) (200), 9.67 (38) (002), 7.30 (29) (202), 4.816 (31) (111, 004), 3.432 (18) (600, 114, 404, 313), 3.197 (18) (510, 511, 006, 314, 602), 3.071 (34) (314, 115). [ABSTRACT FROM AUTHOR]

Single crystals of a novel Bi Ni phosphate Ni(BiO) 2 (PO 4 )(OH) were synthesized by a hydrothermal method in Bi 2 O 3 NiO K 2 O P 2 O 5 system and characterized by X-ray structure analysis and IR and Raman spectroscopy. This compound crystallizes in a namibite type structure with triclinic unit-cell parameters, a = 6.3220 (3) Å, b = 6.9043 (4) Å, c = 7.5641 (5) Å, α = 90.483 (5)°, β = 107.219 (5)°, γ = 110.758 (5)°; V = 292.51 (3) Å 3 ; space group P 1 ¯ (No. 2). Crystal structure is refined to final R 1 = 4.09 using 1637 I > 2σ( I ). The structure contains infinite chains {Ni(OH)(PO 4 )} ∞ built of corner-sharing NiO 6 octahedra. Microscopic calculations of the intra- and interchain J (Ni Ni) exchange parameters suggests possible S = 1 antiferromagnet chain behavior of this compound at low temperatures. [ABSTRACT FROM AUTHOR]

Vesuvianite containing 5.85 wt% TiO2 from an Alpine-cleft-type assemblage outcropped near Alchuri, Shigar Valley, Northern Areas, Pakistan, has been investigated by means of electron microprobe analyses, gas-chromatographic analysis of H2O, X-ray powder diffraction, single-crystal X-ray structure refinement, 27Al NMR, 57Fe Mössbauer spectroscopy, IR spectroscopy and optical measurements. Tetragonal unit-cell parameters are: a = 15.5326 (2), c = 11.8040 (2) Å , space group P4/nnc. The structure was refined to final R1 = 0.031, wR2 = 0.057 for 11247 I > 2σ(I). A general crystal-chemical formula of studied sample can be written as follows (Z = 2): [8-9](Ca17.1Na0.9) [8]Ca1.0 [5](Fe2+0.44Fe3+0.34Mg0.22) [6](Al3.59Mg0.41) [6](Al4.03Ti2.20Fe3+1.37Fe2+0.40) (Si18O68) [(OH)5.84O2.83F1.33]. The octahedral site Y2 is Al-dominant and does not contain transition elements. Another octahedral site Y3 is also Al-dominant and contains Fe2+, Fe3+ and Ti. The site Y1 is split into Y1a and Y1b predominantly occupied by Fe2+ and Fe3+, respectively. The role of the Y1 site in the diversity of vesuvianite-group minerals is discussed. [ABSTRACT FROM AUTHOR]

The new oxalate mineral antipinite is found in a guano deposit located on the Pabellón de Pica Mountain, Iquique Province, Tarapacá Region, Chile. Associated minerals are halite, salammoniac, chanabayaite, joanneumite and clays. Antipinite occurs as blue, imperfect, short prismatic crystals up to 0.1 mm × 0.1 mm × 0.15 mm in size, as well as their clusters and random aggregates. The mineral is brittle. Mohs hardness is 2; Dmeas = 2.53(3), Dcalc = 2.549 g cm-3. The infrared spectrum shows the presence of oxalate anions and the absence of absorptions associated with H2O molecules, C-H bonds, CO32-,NO-3 - and OH- ions. Antipinite is optically biaxial (+), α = 1.432(3), β = 1.530(1), γ = 1.698(5), 2Vmeas = 75(10)°, 2Vcalc = 82°. The chemical composition (electron-microprobe data, C measured by gas chromatography of products of ignition at 1200°C, wt.%) is Na2O 15.95, K2O 5.65, CuO 27.34, C2O3 48.64, total 99.58. The empirical formula is K0.96Na2O4Cu2.03(C2.00O4)4 and the idealized formula is KNa3Cu2(C2O4)4. The crystal structure was solved and refined to R = 0.033 based upon 4085 unique reflections with I > 2σ(I ). Antipinite is triclinic, space group P1, a = 7.1574(5), b = 10.7099(8), c = 11.1320(8) Å, α = 113.093(1), β = 101.294(1), γ = 90.335 (1)°, V = 766.51(3) Å3, Z = 2. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I,%) (hkl)] are 5.22 (40) (11̅1), 3.47 (100) (03̅ 2), 3.39 (80) (2̅10), 3.01 (30) (03̅3, 220), 2.543 (40) (122, 03̅ 4, 104), 2.481 (30) (2̅13), 2.315 (30) (14̅3, 3̅ 10), 1.629 (30) (14̅6, 4̅14̅, 2̅43, 1̅60). [ABSTRACT FROM AUTHOR]

A new hydrogen-containing Ca9(Fe0.63Mg0.37)H0.37(PO4)7 phosphate with the whitlockite-type structure has been synthesized by a hydrothermal method and its structure has been studied by the single-crystal X-ray diffraction. The compound crystallizes in the trigonal space group R3 c (traditional for compounds with the whitlockite-type structure) with unit-cell parameters: a=10.3533(1) Å, c=37.1097(4) Å. The structure has been determined using the 'charge flipping' method. Ca9(Fe0.63Mg0.37)H0.37(PO4)7 structure is similar to that of other members of the whitlockite-type family. The presence of hydrogen in the structure leads to the formation of OH-group with one of the oxygen of PO4-tetrahedra. Based on an analysis of the bond valence sums (BVS) a conclusion has been made about localization of H atoms in the structure. Smaller values of BVS for O1 and O10 atoms than ones for other oxygen atoms indicate localization of H atoms between them in a position with site symmetry 18 b. [ABSTRACT FROM AUTHOR]

In situ thermo‐Raman spectroscopy is used to study a single crystal of natural orthorhombic cubanite from the Talnakh copper‐nickel sulfide deposit (Norilsk, Russia). The dependence of the wavenumbers and FWHMs of vibrational modes on temperature, including the cubanite → isocubanite phase transition region, is studied in the range of 83–873 K. For the first time, the polarized Raman spectra of cubanite have been interpreted according to ab initio calculations performed using the density functional theory (DFT) implemented in the VASP package. In spite of the tetrahedral environment of Cu and Fe atoms in cubanite, the spectra demonstrate the presence of different types of bending (twisting, wagging, scissoring, etc.) and stretching vibrations in two different triatomic (S2‐Cu‐S2) and (Fe‐S1‐Fe) fragments for Ag and B2g symmetries, and in three‐ and four‐atomic (S1‐Cu‐S1) and FeS(2)3 fragments, respectively, for B1g and B3g symmetries. [ABSTRACT FROM AUTHOR]

Calcinaksite, KNa[Ca(H2O)][Si4Ol0], a new natural member of the litidionite group, was found in a calcic xenolith from alkaline basalt of the Bellerberg volcano, Eastern Eifel region, Rhineland-Palatinate, Germany. The crystal structure has been studied based on single-crystal X-ray diffraction data. Triclinic unit-cell parameters are: a = 7.021 (2), b = 8.250 (3), c = 10.145 (2) Å, α = 102.23 (2), β = 100.34 (2), γ = 115.09 (3)°, space group . The structure model was determined by the `charge-flipping' method and refined to R = 0.0527 in anisotropic approximation using 3057 I > 3σ( I). Calcinaksite is a hydrous calcium-dominant litidionite-group mineral. The crystal structure of calcinaksite (like other litidionite-group minerals and related compounds) is based on a heteropolyhedral framework and is characterized by the presence of several types of channels. Calcium forms distorted CaO5Ø (Ø = H2O) octahedra while Na forms NaO5 square pyramids. Nine-coordinated K atoms are located in a channel extending along [010]. Water molecules occupy a channel running along the [100] direction and are characterized by a rather high equivalent isotropic displacement parameter of 0.053 (2) Å2. In calcinaksite, there are three short distances between the water molecule and oxygen atoms, O w...O3 [2.844 (5) Å], O w...O9 [2.736 (4) Å] and O w...O w [2.843 (7) Å]. These distances correspond to three hydrogen bonds detected by IR data (the bands at 3340, 3170 and 3540 cm−1). [ABSTRACT FROM AUTHOR]

Emmerichite Ba Na Fe 3Ti (Si O ) O F , a new mineral of the lamprohyllite group, was found in alkaline basalts at the mountain Rother Kopf, near Gerolstein, Eifel Mountains (Rheinland-Pfalz, Germany) in association with nepheline, leucite, augite, phlogopite, fluorapatite, götzenite, akermanite, günterblassite, magnetite and perovskite. The crystal structure has been studied by single-crystal X-ray diffraction data. Mono­clinic unit-cell parameters are: a= 19.9601(3) Å, b= 7.0989(1) Å, c= 5.4074(1) Å, β= 96.367(1)°, space group C2/ m. Structure model was determined by charge flipping method and refined to R= 4.57% in anisotropic approximation using 4400 F> 4 σF. The structure of emmerichite is similar to that of other members of the lamprophyllite group and is based on the HOH-modules. The main structural and chemical feature of emmerichite is the predominance of Fe 3in the octahedral M3 site. Thus, it is the first Fe 3-dominant titanium member of the lamprophyllite group. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new K, Eu-silicate was synthesized using hydrothermal techniques. [•] The X-ray structure analysis was performed using single crystal diffraction data. [•] The new compound represents the new structure type. [Copyright &y& Elsevier]

Borophosphates of transition 3d metals are based on the mixed heteropolyhedral MTT - or MTTTr -type frameworks formed by M Ø 6 octahedra, two types of T Ø tetrahedra (PO 4 and BO 4 tetrahedra), and, more rarely, Tr O 3 triangles (BO 3 triangles). Family of compounds with the general formula A 1 − x + B x 2 + { M x 2 + M 1 − x 3 + [BP 2 O 8 (OH)]} (where A + ​= ​K, Rb, Cs, NH 4 , B 2+ = Ba, Pb, M 2+ ​= ​Fe, Co, Zn, and M 3+ ​= ​Al, Ga, V3+, Fe3+, Sc, In; x ​= ​0, 1) includes monoclinic (space group P 2 1 / c) and triclinic (space group P 1 ¯) borophosphates. Single crystals of Rb{V[BP 2 O 8 (OH)]} were synthesized by a hydrothermal method. The crystal structure was studied by single-crystal X-ray diffraction analysis: space group P 2 1 / c (No. 15), a ​= ​9.3699(8), b ​= ​8.3162(7), c ​= ​9.6707(8) Å, β ​= ​102.073(9); V ​= ​736.89(11) Å3. The crystal structure of Rb{V[BP 2 O 8 (OH)]} was refined to the final R ​= ​4.52%. A topological description of both structure types of the A 1 − x + B x 2 + { M x 2 + M 1 − x 3 + [BP 2 O 8 (OH)]} compounds and related vanadium-containing phases is given. Because these compounds are characterized by the microporous crystal structures, the possible migration paths for different alkaline ions have been calculated. Family of compounds with the general formula A 1 − x + B x 2 + { M x 2 + M 1 − x 3 + [BP 2 O 8 (OH)]} includes monoclinic (space group P 2 1 / c) and triclinic (space group P 1 ¯) borophosphates.A topological description of both structure types and related vanadium-containing phases is given.The possible migration paths for different alkaline ions have been calculated. [Display omitted] • A topological description of both structure types of the A 1 − x + B x 2 + { M x 2 + M 1 − x 3 + [BP 2 O 8 (OH)]} compounds and related vanadium-containing phases is given. • The possible migration paths for different alkaline ions have been calculated. [ABSTRACT FROM AUTHOR]

Based on Krivovichev information measures for crystal structures and the universal partitioning scheme for different sources of information described previously by Hornfeck, a ladder of information for crystal structures with primary motifs of different dimensionalities (0D, 1D, or 2D) is proposed. Ethanol (0D), SnIP (1D), and TlOH (2D) are discussed as examples of the introduced concept. The proposed calculation technique allows to explicitly obtain contributions of substructures of ordered structures into the information content of a structure conforming to the rule of strong additivity, thus giving a simple assessment of complexity at different hierarchical levels of organization, and takes into account partitioning contacts formed by structural units into equivalence classes, which is poorly dependent on that of the structural units themselves. The technique is a complementation to the multilevel topological analysis performed in the ToposPro program package. [ABSTRACT FROM AUTHOR]

A series of novel phosphates with the general formulas Ca9Gd0.9−xTm0.1Smx(PO4)7 and Ca9Gd0.9−yTmySm0.1(PO4)7 were synthesized by solid-state method. As-obtained phosphates were characterized by powder X-ray diffraction and second harmonic generation analyses, dielectric measurements, luminescence spectroscopy. All samples were single phase and characterized by the whitlockite-type structure with space group R3c. An influence of admixture concentration of REE3+ ions in the initial host on dielectric properties was studied in details. Synthesized phosphates are characterized by intensive luminescence. The emission in the orange region of the visible spectrum is observed for Ca9Gd0.9Sm0.1(PO4)7 with a maximum intensity band at 602 nm. The line in blue region at 455 nm, which corresponds to 1D2 → 3F4 Tm3+ transition, is registered for Ca9Gd0.9Tm0.1(PO4)7. Emission in the white region of CIE coordinates was registered for Tm-Sm co-doped compounds. [ABSTRACT FROM AUTHOR]

The crystal structure of a new polymorph of metaboric acid, δ-HBO2 (s.g. Pnma, a = 14.7578(9), b = 9.3973(5), c = 3.6352(2) Å) is described. The structure consists of flat six-membered B3O3(OH)3 rings forming chains linked to each other by hydrogen bonds. Also, the stability of δ-HBO2 phase was investigated. [ABSTRACT FROM AUTHOR]

The article describes the results of a comprehensive study of the extra-framework components of scapolites using quantum–chemical calculations, electronic and vibrational spectroscopy, and single-crystal X-ray diffraction and crystal structure refinement. The ab initio calculations were performed using an embedded-cluster approach of extra-framework components in various cation surroundings. As a result, through comparing the experimental and ab initio calculation results, the energies of the electronic and vibrational transitions of various extra-framework components (CO3)2−, (CO3) · − , S 3 · − , S 2 · − —as well as the role of these components in the process of the lowering of the symmetry—were determined for scapolites belonging to the marialite–meionite solid–solution series. The nature of the various colors of the scapolites has also been established. Colors from purple to blue are a result of the presence of radiation-induced pairs of defects: carbonate radical anions (CO3) · − and F-centers. However, polysulfide S 3 · − radical anions are found in some violet scapolites. [ABSTRACT FROM AUTHOR]

The crystal structures of compounds with the general formula Cs{[6]Al2[[4]TP6O20]} (where T = Al, B) display order-disorder (OD) character and can be described using the same OD groupoid family. Their structures are built up by two kinds of nonpolar layers, with the layer symmetries Pc(n)2 (L2n+1-type) and Pc(a)m (L2n-type) (category IV). Layers of both types (L2n and L2n+1) alternate along the b direction and have common translation vectors a and c (a ~ 10.0 Å, c ~ 12.0 Å). All ordered polytypes as well as disordered structures can be obtained using the following partial symmetry operators that may be active in the L2n type layer: the 21 screw axis parallel to c [– – 21] or inversion centers and the 21 screw axis parallel to a [21 – –]. Different sequences of operators active in the L2n type layer ([– – 21] screw axes or inversion centers and [21 – –] screw axes) define the formation of multilayered structures with the increased b parameter, which are considered as non-MDO polytypes. The microporous heteropolyhedral MT-frameworks are suitable for the migration of small cations such as Li+, Na+ Ag+. Compounds with the general formula Rb{[6]M3+[[4]T3+P6O20]} (M = Al, Ga; T = Al, Ga) are based on heteropolyhedral MT-frameworks with the same stoichiometry as in Cs{[6]Al2[[4]TP6O20]} (where T = Al, B). It was found that all the frameworks have common natural tilings, which indicate the close relationships of the two families of compounds. The conclusions are supported by the DFT calculation data. [ABSTRACT FROM AUTHOR]

Ion-exchange properties of natural caryochroite (Na,Sr) 3 {(Fe,Mg)2+ 10 (OH) 6 [TiO(Si 6 O 17)(OH) 0.5 ] 2 }·8H 2 O, a microporous heterophyllosilicate with a one-dimensional system of broad zeolytic channels, related to nafertisite Na 3 {Fe2+ 10 (OH) 6 [TiO(Si 6 O 17)F 0.5 ] 2 }·2H 2 O, were studied in reactions with 1 N aqueous solutions of Rb, Cs, Ag, and Pb nitrates at 50 °C. In reactions with Rb+, Cs+, and Pb2+, sodium is partly replaced by nearly equivalent amounts of larger cations. In reactions with Pb2+ and Ag+, additional processes involving H 2 O molecules take place: replacement of two H 2 O molecules with Pb2+ + 2OH− and replacement of H 2 O molecule with Ag+ + OH−, respectively. The geometrical-topological analysis of ion migration pathways in the nafertisite-type structures carried out using an approach based on the Voronoi-Dirichlet partition has shown that only Na+ cations occurring at the centers of wide channels can take part in reactions with large alkaline cations proceeding in counter flows. In the reaction with Ag+, additional Na+ ions are involved. Li+ cations having a smaller radius can pass through the window between the channels, forming a 2D conducting layer. Image 1 • Ion-exchange properties of natural titanosilicate caryochroite, a microporous heterophyllosilicate with a one-dimensional system of broad zeolytic channels, were studied in reactions with 1 N aqueous solutions of Rb, Cs, Ag, and Pb nitrates at 50 °C. • Three kinds of Na+ cations in the caryochroite structure play different role in ion migration processes. • Li+ cations having a smaller radius can pass through the window between the channels, forming a 2D conducting layer. [ABSTRACT FROM AUTHOR]

The new eudialyte-group mineral, odikhinchaite, was discovered in a peralkaline pegmatite vein hosted by melteigite at the Odikhincha ultrabasic alkaline–carbonatite intrusion, Taimyr Peninsula, Krasnoyarsk Krai, Russia. Associated minerals are orthoclase, albite, aegirine, cancrinite, ancylite-(Ce), catapleiite, and wadeite. Odikhinchaite occurs as dense rosette-like aggregates up to 11 mm across, consisting of split lamellar individuals. The mineral is translucent to transparent, deep purple, with vitreous luster. Odikhinchaite is brittle, with uneven fracture; distinct cleavage on (001) is observed. Hardness determined by the micro-indentation method is equal to 430 kgf/mm2; the Mohs hardness is 5. D(meas.) is 2.97(1) g·cm−3, D(calc.) is 3.04 g·cm–3. Odikhinchaite is optically uniaxial (–), ω = 1.638(2), ε = 1.630(2). The IR spectrum shows the presence of the IVMn2+O4 polyhedra, H2O molecules and CO32– anions. The chemical composition is (electron microprobe, H2O determined by the modified Penfield method, CO2 determined by selection sorption of gaseous annealing products; wt%): Na2O 9.25, K2O 0.59, CaO 12.77, MnO 5.49, FeO 0.75, MgO 0.24, La2O3 0.38, Ce2O3 0.39, Nd2O3 0.15, Al2O3 0.07, SiO2 44.80, ZrO2 11.13, TiO2 0.07, Nb2O5 4.17, Cl 0.69, CO2 0.90, H2O 2.22, –O = Cl –0.16, total 99.72. The crystal structure was solved using single-crystal X-ray diffraction data. Odikhinchaite is trigonal, space group R3m; the unit-cell parameters are: a = 14.2837(2) Å, c = 30.0697(3) Å, V = 5313.04(12) Å3. The new mineral is isostructural with other 12-layered members of the eudialyte group with the space group R3m. Its crystal chemical formula is (Z = 3): {N1(Na2.58Ca0.42)N2[Na2.37Ca0.51(H2O)0.12]N3(Sr2.00K0.45Na0.35REE0.20)N4Na3N5[(H2O)1.8Na1.2]}{ZZr3M1Ca6M2(Mn2.49Fe2+0.51)[M3Nb(OH)1.82O1.18](M4SiOH)[Si3O9]2[Si9O27]2X1[(CO3)0.53Cl0.47]X2[(H2O)0.6(O,F)0.4]XM4(CO3)0.15. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 11.42 (64) (101), 4.309 (41) (205), 3.405 (53) (131), 3.208 (45) (208, 036), 3.167 (44) (217), 2.978 (100) (315), 2.858 (86) (404). [ABSTRACT FROM AUTHOR]

Eudialyte-group minerals are important accessory minerals of peralkaline rocks of nepheline-syenite massifs and alkaline–ultramafic complexes. Here, we report the complex study of a eudialyte-group mineral (EGM) from peralkaline pegmatite of the alkaline-ultrabasic Odikhincha massif (Polar Siberia). The chemical composition of the studied EGM is intermediate between those of taseqite and eudialyte, with small admixtures of other members of the eudialyte group. The crystals of EGMs were formed during the postmagmatic stage in the temperature range of 300–350 °C and partly replaced by late eudialite along cracks during the zeolite stage (~230 °C). The chemical compositions, structural features and mineral association of the studied EGM are similar to those of Sr-Nb-dominant EGM found in other nepheline-syenite massifs, such as Khibiny, Lovozero and Pilansberg. The EGM studied in this work is a Cl-deficient taseqite variety ("monochlore taseqite"), which differs from "dichlorotaseqite" (found only in the Ilimaussaq massif) by a lower amount of chlorine. [ABSTRACT FROM AUTHOR]