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1.
Magnetisation measurements were performed on the synthetic analogue of stannite, Cu2FeSnS4, in order to characterise the antiferromagnetic transition at low temperature, evidenced by Bernardini et al. (2000). Temperature and field dependence of the material were checked by means of static magnetisation measurements, carried out scanning the magnetic fields up to 12 T and temperatures in the range 1.4–20 K, while ac susceptibility data were collected at different frequencies ranging from 1.8 to 510 Hz. Both static and dynamic magnetisation data, performed above and below the Néel temperature, 6.1(2) K, confirm stannite to order antiferromagnetically at a long-range scale. Moreover, an increase of both the magnetic anisotropy and the exchange interaction, with respect to the Mn-analogue (Fries et al. 1997), has been observed.  相似文献   

2.
The crystal structure of the unstable mineral alumoklyuchevskite K3Cu3AlO2(SO4)4 [monoclinic, I2, a = 18.772(7), b = 4.967(2), c = 18.468(7) Å, β = 101.66(1)°, V = 1686(1) Å] was refined to R 1 = 0.131 for 2450 unique reflections with F ≥ 4σF hkl. The structure is based on oxocentered tetrahedrons (OAlCu 3 7+ ) linked into chains via edges. Each chain is surrounded by SO4 tetrahedrons forming a structural complex. Each complex is elongated along the b axis. This type of crystal structure was also found in other fumarole minerals of the Great Tolbachik Fissure Eruption (GTFE, Kamchatka Peninsula, Russia, 1975–1976), klyuchevskite, K3Cu3Fe3+O2(SO4)4; and piypite, K2Cu2O(SO4)2.  相似文献   

3.
Crystals of hydronium jarosite were synthesized by hydrothermal treatment of Fe(III)–SO4 solutions. Single-crystal XRD refinement with R1=0.0232 for the unique observed reflections (|Fo| > 4F) and wR2=0.0451 for all data gave a=7.3559(8) Å, c=17.019(3) Å, Vo=160.11(4) cm3, and fractional positions for all atoms except the H in the H3O groups. The chemical composition of this sample is described by the formula (H3O)0.91Fe2.91(SO4)2[(OH)5.64(H2O)0.18]. The enthalpy of formation (Hof) is –3694.5 ± 4.6 kJ mol–1, calculated from acid (5.0 N HCl) solution calorimetry data for hydronium jarosite, -FeOOH, MgO, H2O, and -MgSO4. The entropy at standard temperature and pressure (So) is 438.9±0.7 J mol–1 K–1, calculated from adiabatic and semi-adiabatic calorimetry data. The heat capacity (Cp) data between 273 and 400 K were fitted to a Maier-Kelley polynomial Cp(T in K)=280.6 + 0.6149T–3199700T–2. The Gibbs free energy of formation is –3162.2 ± 4.6 kJ mol–1. Speciation and activity calculations for Fe(III)–SO4 solutions show that these new thermodynamic data reproduce the results of solubility experiments with hydronium jarosite. A spin-glass freezing transition was manifested as a broad anomaly in the Cp data, and as a broad maximum in the zero-field-cooled magnetic susceptibility data at 16.5 K. Another anomaly in Cp, below 0.7 K, has been tentatively attributed to spin cluster tunneling. A set of thermodynamic values for an ideal composition end member (H3O)Fe3(SO4)2(OH)6 was estimated: Gof= –3226.4 ± 4.6 kJ mol–1, Hof=–3770.2 ± 4.6 kJ mol–1, So=448.2 ± 0.7 J mol–1 K–1, Cp (T in K)=287.2 + 0.6281T–3286000T–2 (between 273 and 400 K).  相似文献   

4.
During the production of hydrocarbons from subterranean reservoirs, scaling with calcium carbonate and barium sulfate causes flux decline and dangerous problems in production facilities. This work is intended to study the effect of calcium ions on the precipitation of barium sulfate (barite); then, the effect of the formed barite on calcium carbonate crystallization. The conductometric and pH methods were used to follow the progress of the precipitation reaction in aqueous medium. The obtained precipitates were characterized by FTIR, RAMAN, SEM, and XRD. It was shown that Ca2+ in the reaction media does not affect the microstructure of barite even for higher calcium–barium molar ratio. It influences the precipitation kinetics and the solubility of barite by the formation of CaSO4° ion pairing as a predominant role of complex formation (CaSO4) and the increase of the ionic strength. In Ca(HCO3)2-BaSO4-NaCl aqueous system, experiments have showed that added or formed barite in the reaction media accelerates calcite precipitation. No effect on the microstructure of heterogeneous formed calcite which remain calcite shape. However the presence of carbonate ions affects slightly the microstructure of barite.  相似文献   

5.
Zinclipscombite, a new mineral species, has been found together with apophyllite, quartz, barite, jarosite, plumbojarosite, turquoise, and calcite at the Silver Coin mine, Edna Mountains, Valmy, Humboldt County, Nevada, United States. The new mineral forms spheroidal, fibrous segregations; the thickness of the fibers, which extend along the c axis, reaches 20 μm, and the diameter of spherulites is up to 2.5 mm. The color is dark green to brown with a light green to beige streak and a vitreous luster. The mineral is translucent. The Mohs hardness is 5. Zinclipscombite is brittle; cleavage is not observed; fracture is uneven. The density is 3.65(4) g/cm3 measured by hydrostatic weighing and 3.727 g/cm3 calculated from X-ray powder data. The frequencies of absorption bands in the infrared spectrum of zinclipscombite are (cm?1; the frequencies of the strongest bands are underlined; sh, shoulder; w, weak band) 3535, 3330sh, 3260, 1625w, 1530w, 1068, 1047, 1022, 970sh, 768w, 684w, 609, 502, and 460. The Mössbauer spectrum of zinclipscombite contains only a doublet corresponding to Fe3+ with sixfold coordination and a quadrupole splitting of 0.562 mm/s; Fe2+ is absent. The mineral is optically uniaxial and positive, ω = 1.755(5), ? = 1.795(5). Zinclipscombite is pleochroic, from bright green to blue-green on X and light greenish brown on Z (X > Z). Chemical composition (electron microprobe, average of five point analyses, wt %): CaO 0.30, ZnO 15.90, Al2O3 4.77, Fe2O3 35.14, P2O5 33.86, As2O5 4.05, H2O (determined by the Penfield method) 4.94, total 98.96. The empirical formula calculated on the basis of (PO4,AsO4)2 is (Zn0.76Ca0.02)Σ0.78(Fe 1.72 3+ Al0.36)Σ2.08[(PO4)1.86(AsO4)0.14]Σ2.00(OH)1. 80 · 0.17H2O. The simplified formula is ZnFe 2 3+ (PO4)2(OH)2. Zinclipscombite is tetragonal, space group P43212 or P41212; a = 7.242(2) Å, c = 13.125(5) Å, V = 688.4(5) Å3, Z = 4. The strongest reflections in the X-ray powder diffraction pattern (d, (I, %) ((hkl)) are 4.79(80)(111), 3.32(100)(113), 3.21(60)(210), 2.602(45)(213), 2.299(40)(214), 2.049(40)(106), 1.663(45)(226), 1.605(50)(421, 108). Zinclipscombite is an analogue of lipscombite, Fe2+Fe 2 3+ (PO4)2(OH)2 (tetragonal), with Zn instead of Fe2+. The mineral is named for its chemical composition, the Zn-dominant analogue of lipscombite. The type material of zinclipscombite is deposited in the Mineralogical Collection of the Technische Universität Bergakademie Freiberg, Germany.  相似文献   

6.
In the olivine crystal structure, cations are distributed over two inequivalent octahedral sites, M1 and M2. Kinetics of cation exchange between the two octahedral sites in (Co0.1Mg0.9)2SiO4 single crystal have been studied in the temperature range from 600 to 800°C by monitoring the time evolution of the absorbance of Co2+ ions in M1 or M2 sites using optical spectroscopy after rapid temperature jumps. It was found from such temperature-jump induced relaxation experiments that with increasing temperature the absorbance of Co2+ ions in the M1 site decreases while that in the M2 site increases. This indicates a tendency of Co2+ cations to populate the M2 site with increasing temperatures and vice versa. The experimental relaxation data can be modeled using a triple exponential equation based on theoretical analysis. Activation energies of 221 ± 4 and 213 ± 10 kJ/mol were derived from relaxation experiments on the M2 site and M1 site, respectively, for the cation exchange processes in (Co0.1Mg0.9)2SiO4 olivine. Implications for cation diffusion at low temperatures are discussed.  相似文献   

7.
We present results from low-temperature heat capacity measurements of spinels along the solid solution between MgAl2O4 and MgCr2O4. The data also include new low-temperature heat capacity measurements for MgAl2O4 spinel. Heat capacities were measured between 1.5 and 300 K, and thermochemical functions were derived from the results. No heat capacity anomaly was observed for MgAl2O4 spinel; however, we observe a low-temperature heat capacity anomaly for Cr-bearing spinels at temperatures below 15 K. From our data we calculate standard entropies (298.15 K) for Mg(Cr,Al)2O4 spinels. We suggest a standard entropy for MgAl2O4 of 80.9 ± 0.6 J mol−1 K−1. For the solid solution between MgAl2O4 and MgCr2O4, we observe a linear increase of the standard entropies from 80.9 J mol−1 K−1 for MgAl2O4 to 118.3 J mol−1 K−1 for MgCr2O4.  相似文献   

8.
Sulfur K-edge x-ray absorption spectra (XANES and EXAFS) and L-edge XANES of sphalerite (ZnS), chalcopyrite (CuFeS2) and stannite (Cu2FeSnS4) have been recorded using synchrotron radiation. The K- and L-edge XANES features are interpreted using a qualitative MO/energy band structure model. The densities of unoccupied states at the conduction bands of sphalerite, chalcopyrite and stannite are determined using S K- and L-edge XANES features (up to 15 eV above the edge), combined with published metal K-edge XANES. The SK- and L-edge XANES also indicate that, for sphalerite, the Fe2+ 3d band at the fundamental gap has little or no bonding hybridization with S 3p and S 3s orbitals; for chalcopyrite, the Cu+ 3d and Fe3+ 3d bands have strong mixing with S 3p and S 3s states, while for stannite the Cu+ 3d band strongly hybridizes with S 3p and S 3s orbitals, but the Fe2+ 3d band does not. The post-edge XANES features (15–50 eV above the edge) of sphalerite, chalcopyrite and stannite are similar. These features are related to the tetrahedral coordination of sulfur in all these structures, and interpreted by a multiple scattering model. The resonance energies from both the K-edge and L-edge XANES for these minerals are well correlated with reciprocal interatomic distances and lattice spaces. Sulfur K-edge EXAFS analyses using Fourier transform and curve fitting procedures are presented. Comparison of the structural parameters from EXAFS with x-ray structure data shows that the first shell bond distances (BD) from EXAFS are usually accurate to ±0.02 Å, and that coordination numbers (CN) are generally accurate to ±20 percent. For sphalerite, EXAFS analysis yields the structure parameters for the first three neighbour shells around a sulfur atom; the BD and CN even for the third shell are in close agreement with the x-ray structure, and the Debye-Waller term decreases from the first shell to the third shell. It is shown that sphalerite (ZnS) is a good model compound for EXAFS analysis of sulfur in chalcogenide glasses and metalloproteins.  相似文献   

9.
Atomistic model was proposed to describe the thermodynamics of mixing in the diopside-K-jadeite solid solution (CaMgSi2O6-KAlSi2O6). The simulations were based on minimization of the lattice energies of 800 structures within a 2 × 2 × 4 supercell of C2/c diopside with the compositions between CaMgSi2O6 and KAlSi2O6 and with variable degrees of order/disorder in the arrangement of Ca/K cations in M2 site and Mg/Al in Ml site. The energy minimization was performed with the help of a force-field model. The results of the calculations were used to define a generalized Ising model, which included 37 pair interaction parameters. Isotherms of the enthalpy of mixing within the range of 273–2023 K were calculated with a Monte Carlo algorithm, while the Gibbs free energies of mixing were obtained by thermodynamic integration of the enthalpies of mixing. The calculated T-X diagram for the system CaMgSi2O6-KAlSi2O6 at temperatures below 1000 K shows several miscibility gaps, which are separated by intervals of stability of intermediate ordered compounds. At temperatures above 1000 K a homogeneous solid solution is formed. The standard thermodynamic properties of K-jadeite (KAlSi2O6) evaluated from quantum mechanical calculations were used to determine location of several mineral reactions with the participation of the diopside-K-jadeite solid solution. The results of the simulations suggest that the low content of KalSi2O6 in natural clinopyroxenes is not related to crystal chemical factors preventing isomorphism, but is determined by relatively high standard enthalpy of this end member.  相似文献   

10.
Mn2+Sb2S4, a monoclinic dimorph of clerite, and benavidesite (Mn2+Pb4Sb6S14) show well-individualized single chains of manganese atoms in octahedral coordination. Their magnetic structures are presented and compared with those of iron derivatives, berthierite (Fe2+Sb2S4) and jamesonite (Fe2+Pb4Sb6S14). Within chains, interactions are antiferromagnetic. Like berthierite, MnSb2S4 shows a spiral magnetic structure with an incommensurate 1D propagation vector [0, 0.369, 0], unchanged with temperature. In berthierite, the interactions between identical chains are antiferromagnetic, whereas in MnSb2S4 interactions between chains are ferromagnetic along c-axis. Below 6 K, jamesonite and benavidesite have commensurate magnetic structures with the same propagation vector [0.5, 0, 0]: jamesonite is a canted ferromagnet and iron magnetic moments are mainly oriented along the a-axis, whereas for benavidesite, no angle of canting is detected, and manganese magnetic moments are oriented along b-axis. Below 30 K, for both compounds, one-dimensional magnetic ordering or correlations are visible in the neutron diagrams and persist down to 1.4 K.  相似文献   

11.
The crystal structure of Pb6Bi2S9 is investigated at pressures between 0 and 5.6 GPa with X-ray diffraction on single-crystals. The pressure is applied using diamond anvil cells. Heyrovskyite (Bbmm, a = 13.719(4) Å, b = 31.393(9) Å, c = 4.1319(10) Å, Z = 4) is the stable phase of Pb6Bi2S9 at ambient conditions and is built from distorted moduli of PbS-archetype structure with a low stereochemical activity of the Pb2+ and Bi3+ lone electron pairs. Heyrovskyite is stable until at least 3.9 GPa and a first-order phase transition occurs between 3.9 and 4.8 GPa. A single-crystal is retained after the reversible phase transition despite an anisotropic contraction of the unit cell and a volume decrease of 4.2%. The crystal structure of the high pressure phase, β-Pb6Bi2S9, is solved in Pna2 1 (a = 25.302(7) Å, b = 30.819(9) Å, c = 4.0640(13) Å, Z = 8) from synchrotron data at 5.06 GPa. This structure consists of two types of moduli with SnS/TlI-archetype structure in which the Pb and Bi lone pairs are strongly expressed. The mechanism of the phase transition is described in detail and the results are compared to the closely related phase transition in Pb3Bi2S6 (lillianite).  相似文献   

12.
Fine-granular (<0.1 mm) flattened colorless transparent crystals of ivsite form white aggregates. The empirical formula (Na2.793Cu0.056)2.849HS2.016O8 is close to the ideal Na3H(SO4)2. The structure was refined up to R = 0.040. Ivsite has a monoclinic symmetry, P21/c, a = 8.655(1) Å, b = 9.652(1) Å, c = 9.147(1) Å, β = 108.76(1)°, V = 723.61(1) Å3, Z = 4. Na atoms occur at six- and seven-fold sites (NaO6 and NaO7); S atoms, in isolated SO4 tetrahedrons; these polyhedrons form a three-dimensional framework. The diagnostic lines of powder diffraction patterns (d[Å]–I–hkl) are 4.010–53–12-1, 3.949–87–012, 3.768–100–210, 3.610–21–20-2, 3.022–22–031, 2.891–42–22-2, 2.764–49–31-1, and 2.732–70–13-1.  相似文献   

13.
Using a diamond-anvil cell and synchrotron X-ray diffraction, the compressional behavior of a synthetic qandilite Mg2.00(1)Ti1.00(1)O4 has been investigated up to about 14.9 GPa at 300 K. The pressure–volume data fitted to the third-order Birch–Murnaghan equation of state yield an isothermal bulk modulus (K T0) of 175(5) GPa, with its first derivative \(K_{T0}^{{\prime }}\) attaining 3.5(7). If \(K_{T0}^{{\prime }}\) is fixed as 4, the K T0 value is 172(1) GPa. This value is substantially larger than the value of the adiabatic bulk modulus (K S0) previously determined by an ultrasonic pulse echo method (152(7) GPa; Liebermann et al. in Geophys J Int 50:553–586, 1977), but in general agreement with the K T0 empirically estimated on the basis of crystal chemical systematics (169 GPa; Hazen and Yang in Am Miner 84:1956–1960, 1999). Compared to the K T0 values of the ulvöspinel (Fe2TiO4; ~148(4) GPa with \(K_{T0}^{{\prime }} = 4\)) and the ringwoodite solid solutions along the Mg2SiO4–Fe2SiO4 join, our finding suggests that the substitution of Mg2+ for Fe2+ on the T sites of the 4–2 spinels can have more significant effect on the K T0 than that on the M sites.  相似文献   

14.
A novel complex continuous system of solid solutions involving vauquelinite Pb2Cu(CrO4)(PO4)(OH), bushmakinite Pb2Al(VO4)(PO4)(OH), ferribushmakinite Pb2Fe3+(VO4)(PO4)(OH), and a phase with the endmember formula Pb2Cu(VO4)(PO4)(H2O) or Pb2Cu(VO4)(РО3ОН)(ОН) is studied based on samples from the oxidation zone of the Berezovskoe, Trebiat, and Pervomaisko-Zverevsky deposits in the Urals, Russia. This is the first natural system in which chromate and vanadate anions show a wide range of substitutions and the most extensive solid solution system involving (CrO4)2– found in nature. The major couple substitution is Cr6+ + Cu2+ ? V5+ + M3+, where M = Fe, Al. The correlation coefficients calculated from 125 point analyses are: 0.96 between V and (Fe + Al), 0.96 between Cr and (Cu + Zn),–0.96 between V and (Cu + Zn),–0.97 between Cr and (Fe + Al), and–0.97 between (Fe + Al) and (Cu + Zn). The substitutions V5+ ? Cr6+ (correlation coefficient–0.98) and to a lesser extent P5+ ? As5+ (correlation coefficient–0.86) occur at two types of tetrahedral sites, whereas the metal–nonmetal/metalloid substitutions, i.e., V or Cr for P or As, are minor. The substitution Fe3+ ? Al3+ is also negligible in this solid solution system.  相似文献   

15.
Batisivite has been found as an accessory mineral in the Cr-V-bearing quartz-diopside metamorphic rocks of the Slyudyanka Complex in the southern Baikal region, Russia. A new mineral was named after the major cations in its ideal formula (Ba, Ti, Si, V). Associated minerals are quartz, Cr-V-bearing diopside and tremolite; calcite; schreyerite; berdesinskiite; ankangite; V-bearing titanite; minerals of the chromite-coulsonite, eskolaite-karelianite, dravite-vanadiumdravite, and chernykhite-roscoelite series; uraninite; Cr-bearing goldmanite; albite; barite; zircon; and unnamed U-Ti-V-Cr phases. Batisivite occurs as anhedral grains up to 0.15–0.20 mm in size, without visible cleavage and parting. The new mineral is brittle, with conchoidal fracture. Observed by the naked eye, the mineral is black and opaque, with a black streak and resinous luster. Batisivite is white in reflected light. The microhardness (VHN) is 1220–1470 kg/mm2 (load is 30 g), the mean value is 1330 kg/mm2. The Mohs hardness is near 7. The calculated density is 4.62 g/cm3. The new mineral is weakly anisotropic and bireflected. The measured values of reflectance are as follows (λ, nm—R max ′ /R min ′ ): 440—17.5/17.0; 460—17.3/16.7; 480—17.1/16.5; 500—17.2/16.6; 520—17.3/16.7; 540—17.4/16.8; 560—17.5/16.8; 580—17.6/16.9; 600—17.7/17.1; 620—17.7/17.1; 640—17.8/17.1; 660—17.9/17.2; 680—18.0/17.3; 700—18.1/17.4. Batisivite is triclinic, space group P \(\overline 1\); the unit-cell dimensions are: a = 7.521(1) Å, b = 7.643(1) Å, c = 9.572(1) Å, α = 110.20°(1), β = 103.34°(1), γ = 98.28°(1), V = 487.14(7) Å3, Z = 1. The strongest reflections in the X-ray powder diffraction pattern [d, Å (I, %)(hkl)] are: 3.09(8)(12\(\overline 2\)); 2.84, 2.85(10)(021, 120); 2.64(8)(21\(\overline 3\)); 2.12(8)(31\(\overline 3\)); 1.785(8)(32\(\overline 4\)), 1.581(10)(24\(\overline 2\)); 1.432, 1.433(10)(322, 124). The chemical composition (electron microprobe, average of 237 point analyses, wt %) is: 0.26 Nb2O5, 6.16 SiO2, 31.76 TiO2, 1.81 Al2O3, 8.20 VO2, 26.27 V2O3, 12.29 Cr2O3, 1.48 Fe2O3, 0.08 MgO, 11.42 BaO; the total is 99.73. The VO2/V2O3 ratio has been calculated. The simplified empirical formula is (V 4.8 3+ Cr2.2V 0.7 4+ Fe0.3)8.0(Ti5.4V 0.6 4+ )6.0[Ba(Si1.4Al0.5O0.9)]O28. An alternative to the title formula could be a variety (with the diorthogroup Si2O7) V8Ti6[Ba(Si2O7)]O22. Batisivite probably pertains to the V 8 3+ Ti 6 4+ [Ba(Si2O)]O28-Cr 8 3+ Ti 6 4+ [Ba(Si2O)]O28 solid solution series. The type material of batisivite has been deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.  相似文献   

16.
Oxyvanite has been identified as an accessory mineral in Cr-V-bearing quartz-diopside meta- morphic rocks of the Slyudyanka Complex in the southern Baikal region, Russia. The new mineral was named after constituents of its ideal formula (oxygen and vanadium). Quartz, Cr-V-bearing tremolite and micas, calcite, clinopyroxenes of the diopside-kosmochlor-natalyite series, Cr-bearing goldmanite, eskolaite-karelianite dravite-vanadiumdravite, V-bearing titanite, ilmenite, and rutile, berdesinskiite, schreyerite, plagioclase, scapolite, barite, zircon, and unnamed U-Ti-V-Cr phases are associated minerals. Oxyvanite occurs as anhedral grains up to 0.1–0.15 mm in size, without visible cleavage and parting. The new mineral is brittle, with conchoidal fracture. Observed by the naked eye, the mineral is black, with black streak and resinous luster. The microhardness (VHN) is 1064–1266 kg/mm2 (load 30 g), and the mean value is 1180 kg/mm2. The Mohs hardness is about 7.0–7.5. The calculated density is 4.66(2) g/cm3. The color of oxyvanite is pale cream in reflected light, without internal reflections. The measured reflectance in air is as follows (λ, nm-R, %): 440-17.8; 460-18; 480-18.2; 520-18.6; 520-18.6; 540-18.8; 560-18.9; 580-19; 600-19.1; 620-19.2; 640-19.3; 660-19.4; 680-19.5; 700-19.7. Oxyvanite is monoclinic, space group C2/c; the unit-cell dimensions are a = 10.03(2), b = 5.050(1), c = 7.000(1) Å, β = 111.14(1)°, V = 330.76(5)Å3, Z = 4. The strongest reflections in the X-ray powder pattern [d, Å, (I in 5-number scale)(hkl)] are 3.28 (5) (20\(\bar 2\)); 2.88 (5) (11\(\bar 2\)); 2.65, (5) (310); 2.44 (5) (112); 1.717 (5) (42\(\bar 2\)); 1.633 (5) (31\(\bar 4\)); 1.446 (4) (33\(\bar 2\)); 1.379 (5) (422). The chemical composition (electron microprobe, average of six point analyses, wt %): 14.04 TiO2, 73.13 V2O3 (53.97 V2O3calc, 21.25 VO2calc), 10.76 Cr2O3, 0.04 Fe2O3, 0.01 Al2O3, 0.02 MgO, total is 100.03. The empirical formula is (V 1.70 3+ Cr0.30)2.0(V 0.59 4+ Ti0.41)1.0O5. Oxyvanite is the end member of the oxyvanite-berdesinskiite series with homovalent isomorphic substitution of V4+ for Ti. The type material has been deposited at the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.  相似文献   

17.
The crystal structure of a new compound, (H3O)[(UO2)(SeO4)(SeO2OH)] (monoclinic, P21/n, a = 8.6682(19), b = 10.6545(16), c = 9.846(2) Å, β = 97.881(17)°, V = 900.7(3) Å3), was solved by direct methods and refined to R 1 = 0.050. The structure contains two symmetrically different Se atoms. The Se1 site is coordinated by three O atoms as is characteristic of Se4+ cations. The Se2 site is coordinated by four O atoms and forms selenate anion SeO 4 2? . The structure is based on selenite-selenate sheets [(UO2)(SeO4)(SeO2OH)]? linked by the interlayer H3O? ions. The sheets are parallel to (101). The structure is compared to that of schmiederite, Pb2Cu2(SeO3)(SeO4)(OH)4.  相似文献   

18.
The crystal structure of a new compound [Mg(H2O)4(SeO4)]2(H2O) (monoclinic, P2 1/a, a = 7.2549(12), b = 20.059(5), c = 10.3934(17) Å, β = 101.989(13), V = 1479.5(5) Å3) has been solved by direct methods and refined to R 1 = 0.059 for 2577 observed reflections with |F hkl | ≥ 4σ|F hkl |. The structure consists of [Mg(H2O)4(SeO4)]0 chains formed by alternating corner-sharing Mg octahedrons and (SeO4)2? tetrahedrons. O atoms of Mg octahedrons that are shared with selenate tetrahedrons are in a trans orientation. The heteropoly-hedral octahedral-tetrahedral chains are parallel to the c axis and undulate within the (010) plane. The adjacent chains are linked by hydrogen bonds involving H2O molecules not bound with M2+ cations.  相似文献   

19.
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20.
The successful synthesis of nanoparticles of Fe-bearing kuramite, (Cu,Fe)3SnS4, is reported in this study. Nanocrystalline powders were obtained through a mild, environmentally friendly and scalable solvothermal approach, in a single run. The sample was the object of a multidisciplinary investigation, including X-ray diffraction and absorption, scanning electron microscopy and microanalysis, electron paramagnetic resonance, diffuse reflectance and Mössbauer spectroscopy as well as SQUID magnetometry. The nanoparticles consist of pure Fe-bearing kuramite, exhibiting tetragonal structure. The valence state of the metal cations was assessed to be Cu+, Sn4+ and Fe3+. The material presents a band gap value of 1.6 eV, which is fully compatible with solar cell applications. The uptake of Fe by nanokuramite opens a compositional field where the physical properties can be tuned. We thus foster the application of Fe-bearing nanokuramite for photovoltaics and energy storage purposes.  相似文献   

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