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1.
Summary Recently several natural and artificial ferric iron sulphate crystal structures have been solved. Sideronatrite, Na2Fe3+(SO4)2(OH)·3H2O, does not provide good crystals for structural purposes. However if we examine crystallographic, chemical and physical data some useful information about the ...Fe–O–S... structural topology can be inferred. In fact this analysis strengthens the hypothesis that there is a {Fe 2 3+ (SO4)4(OH)2} chain in sideronatrite like that found in guildite, Cu2+Fe3+(SO4)2(OH)·4H2O.
Sideronatrit: Ein Mineral mit einer {Fe2(SO4)4(OH)2}-Kette vom Typ Guildit?
Zusammenfassung Kürzlich wurden die Kristallstrukturen mehrerer natürlicher und künstlicher Ferrisulfate gelöst. Sideronatrit, Na2Fe3+(SO4)2(OH)·3H2O, liefert keine für die Strukturuntersuchung gut geeigneten Kristalle. Dennoch erhält man aus der Untersuchung der kristallographischen, chemischen und physikalischen Daten nützliche Information über die ...Fe–O–S...-Topologie der Struktur. Eine solche Analyse spricht für die Hypothese, daß der Sideronatrit eine {Fe 2 3+ (SO4)4(OH2)}-Kette enthält, wie sie im Guildit, Cu2+Fe3+(SO4)2(OH)·4H2O, gefunden wurde.

With 1 Figure

Paper presented at the Sixth European Crystallographic Meeting. Barcelona, Spain 1980.  相似文献   

2.
According to Koopmans' theorem, only the electrons associated with molecular levels of negative energy are stable. Many ions which cannot exist in the isolated state because certain occupied levels are positive, become stable in crystals under the stabilization effect arising from the crystal field. As examples, we have studied CO 3 2? in calcite, NO 3 ? in NaNO3, and several natural limpurities: O 3 ? in fluorite, [(OH)4]4?, [(OH)3F]4? and [(OH)2F2]4? in zircon and thorite, by means of the molecular self-consistent field, the crystal field being simulated by point charges. As expected, all the energies corresponding to the occupied levels are negative within the crystal field, contrary to what occurs in the isolated state. Informations concerning the structure and the size of the critical germ are obtained for CaCO3 and NaNO3.  相似文献   

3.
Summary Based on a X-ray structure analysis it was proved that the mineral schmiederite contains both selenite and selenate groups [a = 9.922(3)Å,b = 5.712(2)Å,c = 9.396(3)Å, = 101.96(3)°, space group P21/m,Z = 2 {Pb2Cu2(OH)4(SeO3)(SeO4)},R w = 0.055 for 1131 reflections up to sin / = 0.65 Å–1]. The crystal structure is closely related to that of linarite [a = 9.701(2) Å,b = 5.650(2) Å,c= 4.690(2)Å, = 102.65(2)°, space group P21/m,Z = 2 {PbCu(OH)2(SO4)},R w = 0.034 for 1991 reflections up to sin / = 1.0 Å–1].The Pb atom in linarite and the Pb(1) atom in schmiederite have each three Pb-O bonds < 2.45 Å with trigonal pyramidal arranged ligands; the Pb(2) atom in schmiederite has only one such near O atom. The Cu atoms are approximately square planar coordinated by hydroxil groups. In addition two further O atoms complete the coordination figure to a strongly distorted octahedron. All the anion groups have the usual geometry.
Kristallstruktur und chemische Formel von Schmiederit, Pb2Cu2(OH)4(SeO3)(SeO4), mit einem Vergleich zu Linarit, PbCu(OH)2(SO4)
Zusammenfassung Basierend auf einer Röntgen-Strukturuntersuchung konnte das Vorliegen von Selenit-und Selenatgruppen im Mineral Schmiederit belegt werden [a=9,922(3) Å,b = 5,712(2) Å,c = 9,396(3) Å, = 101,96(3)°, Raumgruppe P21/m,Z=2 {Pb2Cu2(OH)4(SeO3)(SeO4)},R w = 0,055 für 1131 Reflexe bis sin /, = 0,65 Å–1]. Die Kristallstruktur weist enge Beziehungen zu jener des Linarits auf [a = 9,701(2) Å,b = 5,650(2) Å,c = 4,690(2) Å, = 102,65(2)°, Raumgruppe P21/m,Z=2 {PbCu(OH)2(SO4)},R w = 0,034 für 1991 Reflexe bis sin / = 1,0 Å–1].Das Pb-Atom im Linarit sowie das Pb(1)-Atom im Schmiederit haben jeweils drei Pb-O-Bindungen <,45 Å, wobei die Liganden trigonal pyramidal angeordnet sind; das Pb(2)-Atom im Schmiederit hat hingegen nur ein derart nahes O-Atom. Die Cu-Atome sind etwa quatratisch planar von Hydroxilgruppen koordiniert; zwei weitere O-Atome ergänzen die Koordinationsfigur zur einem stark verzerrten Oktaeder. Die Aniongruppen haben die üblichen Dimensionen.
  相似文献   

4.
The infinite dilution diffusion coefficient for Al(OH)4? necessary to calculate fluxes of dissolved Al between sediments and overlying waters, was determined at 25°C. Measurements were made using the diaphragm-cell method by diffusing Al(OH)4? spiked KBr solutions against KCL over a range of ionic strengths. The mean of 9 separate measurements gives 1.04 ± .02 × 10?5cm2/s as the infinite dilution diffusion coefficient for Al(OH)4? at 25°C.  相似文献   

5.
Inhalt Eine mit zweidimensionalen Fouriermethoden durchgeführte Strukturverfeinerung bestätigt die vonH. Heritsch (1940) für Libethenit bestimmte Struktur. Von der daraus resultierenden kristallchemischen Formel Cu[4+2] Cu[5] (OH) [PO4] ist sowohl die Strukturanalogie mit Andalusit und Adamin als auch die zu gleichen Teilen auftretende Sechser- und Fünferkoordination des zweiwertigen Kupfers in Libethenit abzulesen.

Mit 2 Textabbildungen  相似文献   

6.
Summary The crystal structure of arsentsumebite, ideally, Pb2Cu[(As, S)O4]2(OH), monoclinic, space group P21/m, a = 7.804(8), b = 5.890(6), c = 8.964(8) ?, β = 112.29(6)°, V = 381.2 ?3, Z = 2, dcalc. = 6.481 has been refined to R = 0.053 for 898 unique reflections with I> 2σ(I). Arsentsumebite belongs to the brackebuschite group of lead minerals with the general formula Pb2 Me(XO4)2(Z) where Me = Cu2+, Mn2+, Zn2+, Fe2+, Fe3+; X = S, Cr, V, As, P; Z = OH, H2O. Members of this group include tsumebite, Pb2Cu(SO4)(PO4)(OH), vauquelinite, Pb2Cu(CrO4)(PO4)(OH), brackebuschite, Pb2 (Mn, Fe)(VO4)2(OH), arsenbracke buschite, Pb2(Fe, Zn)(AsO4)2(OH, H2O), fornacite, Pb2Cu(AsO4)(CrO4)(OH), and feinglosite, Pb2(Zn, Fe)[(As, S)O4]2(H2O). Arsentsumebite and all other group members contain M = M–T chains where M = M means edge-sharing between MO6 octahedra and M–T represents corner sharing between octahedra and XO4 tetrahedra. A structural relationship exists to tsumcorite, Pb(Zn, Fe)2(AsO4)2 (OH, H2O)2 and tsumcorite-group minerals Me(1)Me(2)2(XO4)2(OH, H2O)2. Received June 24, 2000; revised version accepted February 8, 2001  相似文献   

7.
Summary The mineral fibroferrite has the chemical formula Fe(OH)SO4·xH2O; the value forx has not been definitely settled, but as a rule it is found to be near five. Several symmetries are given in the literature.A sample from Saint Felix de Paillères, France, proved to be rhombohedral with space group R3; lattice constants for the hexagonal cell area=24.176,c=7.656 Å. As calculated from the experimental density (=1.95 g·cm–3)Z=18 for this cell. Intensities were collected on an automated X-ray diffractometer from a thin fiber extended along [00.1]. The structure was determined by Patterson and Fourier methods. Least squares refinement with 818 observed reflections resulted inR=0.076.The structure contains hydroxo-bridged {Fe(OH)(H2O)2SO4} spiral chains built of [Fe(OH)2(H2O)2O2] octahedra and SO4 tetrahedra. Hydrogen bonds provide connections between these chains. The spiral chains are a stereoisomer variant of the hydroxo-bridged linear chains of Fe(OH)SO4, butlerite and parabutlerite. A comparison of these compounds is givenm to understand the relationship between the structure and their water content.
Fibroferrit: Ein Mineral mit einer {Fe(OH)(H2O)2SO4} Spiralkette und seine Beziehung zu Fe(OH)SO4, Butlerit und Parabutlerit
Zusammenfassung Das Mineral Fibroferrit hat die chemische Formel Fe(OH)SO4·xH2O; der Wert furx scheint nicht endgültig geklärt zu sein, liegt aber meist nahe 5. Verschiedene Symmetrien werden in der Literatur angegeben.Eine Probe von Saint Felix de Paillères, Frankreich, erwies sich als rhomboedrisch mit der Raumgruppe R3; die Gitterkonstanten der hexagonalen Zelle sinda=24,176,c=7,656 Å. Die experimentelle Bestimmung der Dichte (=1,95 g·cm–3) führt für diese Zelle zuZ=18. Von einer nach [00.1] gestreckten dünnen Faser wurden die Intensitäten auf einem automatischen Röntgendiffraktometer gesammelt. Die Struktur wurde mit Patterson-und Fouriersynthesen gelöst. Eine Verfeinerung nach der Methode der kleinsten Quadrate führte für 818 beobachtete Reflexe aufR=0,076.Die Struktur enthält durch Hydroxil-Gruppen verknüpfte {Fe(OH)(H2O)2SO4}-Spiralketten, die aus [Fe(OH)2(H2O)2O2]-Oktaedern und SO4-Tetraedern aufgebaut sind. Die Spiralketten von Fibroferrit sind eine stereoisomere Variante der annähernd linearen Fe–O–S-Ketten von Fe(OH)SO4, Butlerit und Parabutlerit. Diese Verbindungen werden mit Fibroferrit verglichen, um Beziehungen zwischen Struktur und Wassergehalt zu verstehen.

With 2 Figures

Paper presented at the Fifth European Crystallography Meeting, Copenhagen, Denmark 1979.  相似文献   

8.
Zusammenfassung Die Kristallstruktur des Minerals Teschemacherit, NH4CO2(OH), (a=7,255,b=10,709,c=8,746 Å;Z=8, Raumgruppe:Pccn) wurde an synthetischem Material mit 3-dimensionalen Röntgendaten verfeinert. Die Struktur wird aus parallel [001] verlaufenden [CO2(OH)]–-Ketten aufgebaut. Wasserstoffbrücken zu [NH4]+-Gruppen verbinden diese Ketten zu einem 3-dimensionalen Gerüst.
Refinement of the crystal structure of teschemacherite, NH4CO2(OH)
Summary The crystal structure of the mineral teschemacherite, NH4CO2(OH), (a=7.255,b=10.709,c=8.746 Å,Z=8, space group:Pccn) was refined with 3-dimensional X-ray data using synthetic material. The structure is built up by [CO2(OH)–-chains parallel to [001]. Hydrogen bridges of the [NH4]+-group connect these chains to a 3-dimensional network.

Mit 1 Abbildung  相似文献   

9.
Zusammenfassung Die Kristallstruktur des Johannits wurde anhand eines verzwillingten Kristalls von Joachimsthal, Böhmen, mit dreidimensionalen Röntgendaten bestimmt und für 2005 unabhängige Reflexe aufR=0,039 verfeinert. Johannit kristallisiert triklin, RaumgruppeP1, mita=8,903 (2),b=9,499 (2),c=6,812 (2) Å, =109,87 (1) =112,01 (1), =100,40 (1)° undV=469,9 Å3. Chemische Formel und Zellinhalt lauten Cu(UO2)2(OH)2(SO4)2·8H2O, das ist um zwei H2O-Moleküle mehr als bisher angenommen. In der Struktur sind pentagonal dipyramidale (UO2)(OH)2O3-Polyeder paarweise über eine von zwei OH-Gruppen gebildete Kante zu Doppelpolyedern und diese wiederum durch SO4-Gruppen zu (UO2)2(OH)2(SO4)2-Schichten parallel (100) verknüpft. Die Schichten sind parallel über gestreckte Cu(H2O)4O2-Oktaeder und Wassermoleküle miteinander verbunden. Folgende Bindungslängen wurden gefunden: U–O=1,78 Å (2x) und 2,34–2,39 Å (5x); Cu–O=1,97 Å (4x) und 2,40 Å (2x); =1,47 Å; O–O in Wasserstoffbrücken 2,71–2,91 Å (8x) und 3,30 Å.
The crystal structure of johannite, Cu(UO2)2(OH)2(SO4)2·8H2O
Summary The crystal structure of johannite has been determined from threedimensional X-ray data measured on a twinned crystal from Joachimsthal, Böhmen, and has been refined toR=0.039 for 2005 independent reflections. Johannite crystallizes triclinic, space groupP1, witha=8.903 (2),b=9.499 (2),c=6.812 (2) Å, =109.87(1), =112.01(1), =100.40 (1)° andV=469.9 Å3. Chemical formula and cell content are Cu(UO2)2(OH)2(SO4)2·8H2O, by two H2O molecules more than previously assumed. Pairs of pentagonal dipyramidal (UO2) (OH)2O3 polyhedra form double polyhedra by edgesharing via two OH groups. The double polyhedra are linked by the SO4 tetrahedra to form layers (UO2)2(OH)2(SO4)2 parallel zu (100). These layers are interconnected parallel toa by elongated Cu(H2O)4O2 octahedra and water molecules. Following bond lengths have been observed: U–O=1.78 Å (2x) and 2.34–2.39 Å (5x); Cu–O=1.97 Å (4x) and 2.40 Å (2x); =1.47 Å; O–O for hydrogen bonds 2.71–2.91 Å (8x) and 3.30 Å.

Mit 2 Abbildungen  相似文献   

10.
The structure and spectroscopic properties of selected models of B-type carbonate defects in apatite locally compensated by fluoride or hydroxyl ions are investigated using first-principles quantum mechanical calculations. Theoretical infrared absorption spectra and 13C, and 19F nuclear magnetic resonance chemical shifts are determined. Among the investigated models, only the clumped (CO3 2?, F?) defect, with the carbonate group close to the sloping face of the tetrahedral site and the F? ion at the remaining apex, corresponds to previous experimental observations performed on carbonate-fluorapatite samples. Although the substitution of hydroxyl by fluoride ions is commonly observed in minerals, the clumped (CO3 2?, OH?) defects are unlikely to occur in apatite, considering both their theoretical spectroscopic properties and relative stability. Anionic F? for OH? exchange between channel and B sites displays a preference of ~20 kJ/mol for the local charge compensation by fluoride ions at the B-site, pointing to a significantly different behavior of F? and OH? ions in the charge compensation mechanism. This difference is ascribed to the poor H-bond acceptor character of available oxygen atoms surrounding the apex of the tetrahedral site. The explicit calculation of the infrared absorption spectra of the defect models is also used to interpret the significant difference observed in the linewidth of the ν2 and ν3 CO3 infrared powder absorption bands of carbonated apatite samples. It is shown that for a concentration of 4.4 wt% of CO2, long-range electrostatic effects already significantly contribute to the broadening of the ν3 CO3 bands in apatite.  相似文献   

11.
Polarized electronic absorption spectra of colourless chalcocyanite, CuSO4, have been measured using microscope-spectrometric techniques. The spectra are characterized by a structured and clearly polarized band system in the near-infrared spectral range with components centred at 11,720, 10,545, 9,100, and 7,320 cm?1, which have been assigned to crystal field d–d transitions of Cu2+ cations in pseudo-tetragonally elongated CuO6 polyhedra with point symmetry C i ( \(\bar{1}\) ). The polarization behaviour is interpreted based on a D 2(C 2″) pseudo-symmetry. Crystal field calculations were performed for the actual triclinic point symmetry by applying the Superposition Model of crystal fields, as well as in terms of a ‘classic’ pseudo-tetragonal crystal field approach yielding the parameters Dq (eq) = 910, Dt = 395, and Ds = 1,336 cm?1, corresponding to a cubically averaged Dq cub = 679 cm?1. A comparative survey on crystal fields in Cu2+ minerals shows that the low overall crystal field strength in chalcocyanite, combined with a comparatively weak pseudo-tetragonal splitting of energy levels, is responsible for its unique colourless appearance among oxygen-based Cu2+ minerals. The weak crystal field in CuSO4 can be related to the lower position of the SO4 2? anion compared to, e.g. the H2O molecule in the spectrochemical series of ligands.  相似文献   

12.
Total concentrations of and binding capacities for Cd, Cu, and Pb were measured in selected surface waters from northwestern Europe. Linear multiple regression predictive models explained 97, 93, and 96% of the observed variation in Cd, Cu and Pb binding capacities, respectively. The models constructed used (CO23?) and (SO22?) to predict Cd binding capacity, (OH?) and (SO42?) to predict Cu binding capacity and (OH?), (CO32?) and (SO42?) to predict Pb binding capacity. Organic carbon was not significantly correlated with binding capacities for Cd, Cu, and Pb and was unimportant in explaining a significant amount of the variability in binding capacities for the metals of northern European surface waters. Thus, the effects of these organics on trace metal speciation can be ignored and predictive models of trace metal speciation constructed, using inorganic solubility equilibria only. Ratios of total Cd, Cu, and Pb concentrations to their respective binding capacities were much less than unity for all waters studied. Copper exhibited the greatest metal concentrations: binding capacity ratio in all waters investigated.  相似文献   

13.
Polarized single crystal Raman spectra of the langbeinite K2Cd2(SO4)3 were recorded for different polarisations. With a view to understanding the phase transition mechanism, the lattice vibrational spectra (0–300 cm?1), as well as the SO4 symmetric stretching mode v 1 (1,022 cm?1), were recorded at different temperatures. No soft modes were observed. From the study of the temperature variation of the integrated intensity I 0 and band width Γ of the hard mode (1,022 cm?1), both SO4 libration and SO4 order/disorder models were ruled out as possible phase transition models. On the other hand, the model of Speer and Salje (paper I), involving the distortion of the polyhedra around Cd and K ions, explains the observed temperature behaviour of the Raman spectra very well. The consequences of a possible hypothetical high-temperature phase are discussed.  相似文献   

14.
By using a specially designed and constructed isopiestic apparatus, we measured the osmotic coefficients at 313.2 K for the NaOH-NaAl(OH)4-H2O system with the total alkali molality, mNaOHT (mNaOH + mNaAl[OH]4), from 0.05 mol/kg H2O to 12 mol/kg H2O and αK (mNaOHT/mNaAl(OH)4) from 1.64 to 5.53. The mean standard deviation of the measurements is 0.0038. Several sets of the Pitzer model parameters for NaOH-NaAl(OH)4-H2O system were then obtained by regressing the measured osmotic coefficients with the Pitzer model and the Pitzer model parameters for NaOH(aq). One set of the results is as follows: β(0)NaOH: 0.08669, β(1)NaOH: 0.31446, β(2)NaOH: −0.00007367, CΦNaOH: 0.003180, β(0)NaAl(OH)4: 0.03507, β(1)NaAl(OH)4: 0.02401, CΦNaAl(OH)4: −0.001066, θOH−Al(OH)4−: 0.08177, ΨNa+OH−Al(OH)4−: −0.01162. The mean standard difference between the calculated and the measured osmotic coefficients is 0.0088. With the obtained Pitzer model parameters, we calculated the values of K = (γNaAl(OH)4,cal2 · mAl(OH)4−,exp)/(γNaOH,cal2 · mOH−,exp) for the gibbsite solubility. The results show that the obtained Pitzer model parameters are reliable, and the relative error of the calculated activity coefficients should be < 2.1%. We also compared the calculated gibbsite solubility data among several activity coefficients models over a range of mNaOHT at various temperatures. The comparison indicates that our activity coefficients model may be approximately applied in the ranges of temperature from 298.2 to 323.2 K and mNaOHT from 0 to 8 mol/kg H2O. We also calculated the stoichiometric activity coefficients of NaOH and NaAl(OH)4 and the activity of H2O for the NaOH-NaAl(OH)4-H2O system, and these calculations establish their variations with mNaOHT and αK. These variations imply that the strengths of the repulsive interactions among various anions are in the following sequence: Al(OH)4−-Al(OH)4− < Al(OH)4−-OH− < OH−-OH−, and the attractive interaction between Al(OH)4− and H2O is weaker than that between OH− and H2O.  相似文献   

15.
Summary The crystal structure of the tetragonal fumarole mineral nabokoite, Cu7TeO4(SO4)5 · KCl (a=9.833 (1).Å,c=20.591(2) Å, space groupP 4/ncc, Z=4) was determined by single crystal X-ray methods on type material from Kamchatka. The structure contains complicated {[CU7TeO4(SO4)4]SO4} sheets that are intercalated by K and Cl ions. Nabokoite presents the first example of a Te(IV)O4 pyramid with exactly tetragonal symmetry. The K ions have a somewhat unusual, rather flat coordination.
Die Kristallstruktur des Nabokoits, Cu7TeO4(SO4)5 · KCl: Das erste Beispiel für eine Te(IV)O4-Pyramide mit exakt tetragonaler Symmetrie
Zusammenfassung Die Kristallstruktur des tetragonalen Fumarolenminerals Nabokoit, Cu7TeO4(SO4)5 · KCl (a=9,833(1)Å,c=20,591(2)Å, RaumgruppeP 4/ncc, Z=4) wurde an Typ-Material von Kamtschatka mit Röntgen-Einkristallmethoden bestimmt. Die Struktur enthält komplizierte [Cu7TeO4(SO4)4]SO4-Schichten, die durch K- und Cl-Ionen verbunden werden. Nabokoit liefert das erste Beispiel für eine Te(IV)O4-Pyramide mit exakt tetragonaler Symmetrie. Die K-Ionen haben eine etwas ungewöhnliche, ziemlich flache Koordination.

With 2 Figures  相似文献   

16.
A theoretical model was developed to study the chemical speciation of the trace elements Zn, Cd, Cu and Pb aqueous solutions and their responses to variations in ionic strength and complexation. Two mixing solutions were investigated, a freshwater-seawater system and a freshwater-brine system. The brine was a calcium, sodium-chloride solution with a molal ionic strength of two. Trace element associations with the ligands OH?, Cl?, CO2?3, SO2?4, and HCO?3 were considered at pHs from 3.5 to 11.0 at 25°C. In general, the relative importance of the various ligand-trace element complexes can be predicted from a comparison of their stability constants. However, the effect of pH on the importance of a given complex is not readily apparent from the stability constants. Freshwater-seawater mixtures, as might be found in a totally mixed estuary, show that seawater composition is the dominant control on chemical complexing. Chloride complexing is similar for lead and zinc in the freshwater-brine mixtures. This similarity may account in part for the association of lead and zinc in strata-bound ore deposits.  相似文献   

17.
Auriacusite, ideally Fe3+Cu2+AsO4O, is a new arsenate mineral (IMA2009–037) and the Fe3+ analogue of olivenite, from the Black Pine mine, 14.5 km NW of Philipsburg, Granite Co., Montana, USA. It occurs lining quartz vughs and coating quartz crystals and is associated with segnitite, brochantite, malachite, tetrahedrite and pyrite. Auriacusite forms fibrous crystals up to about 5?µm in width and up to about 100?µm in length, which are intergrown to form fibrous mats. Individual crystals are a brownish golden yellow, whilst the fibrous mats are ochreous yellow. The crystals have a silky lustre and a brownish yellow streak. Mohs hardness is about 3 (estimated). The fracture is irregular and the tenacity is brittle. Auriacusite crystals are biaxial (+), with α?=?1.830(5), β?=?1.865(5) and γ?=?1.910(5), measured using white light, and with 2V meas.?=?83(3)º and 2V calc. = 84.6º. Orientation: X?=?a, Y?=?c, Z?=?b. Crystals are nonpleochroic or too weakly so to be observed. The empirical formula (based on 5 O atoms) is (Fe 1.33 3+ Cu0.85Zn0.03)Σ2.21(As0.51Sb0.27Si0.04?S0.02Te0.01)Σ0.85O5. Auriacusite is orthorhombic, space group Pnnm, a?=?8.6235(7), b?=?8.2757(7), c?=?5.9501(5) Å, V?=?424.63(6) Å3, Z?=?4. The five strongest lines in the powder X-ray diffraction pattern are [d obs in Å / (I) / hkl]: 4.884 / (100) / 101, 001; 2.991 / (92) / 220; 2.476 / (85) / 311; 2.416 / (83) / 022; 2.669 / (74) / 221. The crystal structure was solved from single-crystal X-ray diffraction data utilising synchrotron radiation and refined to R 1?=?0.1010 on the basis of 951 unique reflections with F o?>?4σF. Auriacusite is identified as a member of the olivenite group with Fe3+ replacing Zn2+ or Cu2+ in trigonal bipyramidal coordination. Evidence suggests that auriacusite is an intermediate member between olivenite and an as yet undescribed Fe3+Fe3+-dominant member. The name is derived from the Latin auri (golden yellow) and acus (needle), in reference to its colour and crystal morphology.  相似文献   

18.
The computer program PHREEQC was used to determined the distribution, chemical speciation and mineral saturation indices in a fresh groundwater environment with limited mining activities in the adjoining areas. The aim was mainly to determine the potential risk of a coastal plain aquifer contamination by some potentially toxic elements. The results show that the elements Ba, Cd, Cu, Fe, Mn, Ni, Rb, Sr, and Zn are distributed as free metal ions. Arsenic is in the neutral form of H3AsO3 o, while three species of aluminium [Al3+, AlOH2, Al(OH)2 +] dominate. The major species of uranium include UO2CO3, UO22++, UO2+, and UO2OH+, respectively, in order of abundance. The groundwater is saturated with respect to alunite [KAl3 (SO4)2 (OH)6], basaluminite [Al4 (OH)10 SO4], boehmite [Al(OH)], Cu metal (Cu), cuprous ferrite (CuFeO2), diaspore [AlO(OH)], gibbsite [Al(OH)3], goethite (FeOOH), hematite (Fe2O3), magnetite (Fe3O4) and uraninite (UO2). Most of the species are not mobile under the prevailing pH (3.3 to 5.9) and Eh (7 to 158 mV) conditions. The mobile ones are very low in concentration and will be immobilized by precipitation of mineral phases. The study concludes that presently these species do not pose any risk to the aquifer.  相似文献   

19.
Summary Sonoraite, FeTeO3(OH)·H2O, is monoclinic,P 21/c, witha=10.984(2),b=10.268(2),c=7.917(2) Å, =108.49(2)°. For 8 formula units per cell the calculated density is 4.179(2) g/cm3; the observed value is 3.95(1) g/cm3. The Supper-Pace automated diffractometer was used to collect 1884 independent reflections which were corrected for absorption. The structure was determined by an automated symbolic addition procedure. It was refined to a residualR of 6.2% using anisotropic temperature factors for the cations and isotropic temperature factors for the oxygen atoms. Chains of octahedra about Fe extend along [101]; edge-sharing pairs of these octahedra are joined by corner sharing. The Fe–Fe distances across the shared edges are 3.05 and 3.20 Å, short enough to suggest magnetic interactions. All but one H2O are involved in the chains. The Te4+ ions have a pseudotetrahedral coordination, with three oxygen ions forming one face of the tetrahedron and the lone electron pair of Te occupying the fourth corner. The O–Te–O average bond angle is 95°. The Fe chains are tied together by Te–O bonds in all three dimensions.
Die Kristallstruktur von Sonorait, Fe3+Te4+O3(OH).H2O
Zusammenfassung Sonorait, FeTeO3(OH)·H2O, ist monoklin, P 21/c, mit den folgenden Zelldimensionen:a=10,984(2),b=10,268(2),c=7,917(2) Å, =108,49(2)°. Mit 8 Formel-Einheiten errechnet man eine Dichte von 4,179(2) g/cm3; die gemessene Dichte beträgt 3,95(1) g/cm3. Das Supper-Pace automatische Diffraktometer wurde zur Sammlung von 1884 unabhängigen Reflexen benutzt, welche für Absorption korrigiert wurden. Die Struktur wurde mit Hilfe eines vollständig automatischen Programms für symbolische Addition bestimmt. Mit anisotropen Temperaturfaktoren für die Kationen und mit isotropen Temperaturfaktoren für die Sauerstoff-Atome wurde ein Residuum von 6,2% erreicht. Ketten von Eisen-Oktaedern erstrecken sich entlang [101]; Oktaeder-Paare mit gemeinsamen Kanten sind über Eckenverknüpfung verbunden. Die Fe–Fe-Abstände über die gemeinsamen Kanten betragen 3,05 und 3,20 Å, kurz genug, um zu magnetischer Wechselwirkung führen zu können. Nur ein H2O-Molekül ist nicht Teil einer Kette. Die Te4+-Ionen befinden sich in pseudotetraedrischer Koordination; drei Sauerstoff-Ionen bilden eine Fläche des Tetraeders, die vierte Ecke wird durch das einsame Elektronenpaar von Te besetzt. Der Mittelwert des O–Te–O-Bindungswinkels beträgt 95° Die Fe-Ketten werden durch Te–O-Bindungen dreidimensional verbunden.

With 3 Figures  相似文献   

20.
We performed in situ infrared spectroscopic measurements of OH bands in a forsterite single crystal between ?194 and 200 °C. The crystal was synthesized at 2 GPa from a cooling experiment performed between 1,400 and 1,275 °C at a rate of 1 °C per hour under high silica-activity conditions. Twenty-four individual bands were identified at low temperature. Three different groups can be distinguished: (1) Most of the OH bands between 3,300 and 3,650 cm?1 display a small frequency lowering (<4 cm?1) and a moderate broadening (<10 cm?1) as temperature is increased from ?194 to 200 °C. The behaviour of these bands is compatible with weakly H-bonded OH groups associated with hydrogen substitution into silicon tetrahedra; (2) In the same frequency range, two bands at 3,617 and 3,566 cm?1 display a significantly anharmonic behaviour with stronger frequency lowering (42 and 27 cm?1 respectively) and broadening (~30 cm?1) with increasing temperature. It is tentatively proposed that the defects responsible for these OH bands correspond to H atoms in interstitial position; (3) In the frequency region between 3,300 and 3,000 cm?1, three broad bands are identified at 3,151, 3,178 and 3,217 cm?1, at ?194 °C. They exhibit significant frequency increase (~20 cm?1) and broadening (~70 cm?1) with increasing temperature, indicating moderate H bonding. These bands are compatible with (2H)Mg defects. A survey of published spectra of forsterite samples synthesized above 5 GPa shows that about 75 % of the incorporated hydrogen belongs to type (1) OH bands associated with Si substitution and 25 % to the broad band at 3,566 cm?1 (type (2); 3,550 cm?1 at room temperature). The contribution of OH bands of type (3), associated to (2H)Mg defects, is negligible. Therefore, solubility of hydrogen in forsterite (and natural olivine compositions) cannot be described by a single solubility law, but by the combination of at least two laws, with different activation volumes and water fugacity exponents.  相似文献   

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