Abstract
Autunite, Ca[(UO2)(PO4)]2(H2O)11, is amongst the most abundant and widely distributed of the uranyl phosphate minerals, yet because of its pseudo-tetragonal symmetry and rapid dehydration in air, the details of its symmetry, stoichiometry, and structure were previously uncertain. The crystal structure of synthetic autunite was solved by direct methods and refined by full-matrix least-squares techniques to agreement indices R1 = 0.041, calculated for the 1497 unique observed reflections (|F0| ≥ 4σF), and wR2 = 0.119 for all data. Autunite is orthorhombic, space group Pnma, Z = 4, a = 14.0135(6), b = 20.7121(8), c = 6.9959(3) Å, V = 2030.55(15) Å3. The structure contains the wellknown autunite type sheet with composition [(UO2)(PO-)]-, resulting from the sharing of equatorial vertices of the uranyl square bipyramids with the phosphate tetrahedra. The calcium atom in the interlayer is coordinated by seven H2O groups and two longer distances to uranyl apical O atoms. Two symmetrically independent H2O groups are held in the structure only by hydrogen bonding. Bond-length-constrained refinement provided a crystal-chemically reasonable description of the hydrogen bonding.
© 2015 by Walter de Gruyter Berlin/Boston
Artikel in diesem Heft
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- The effect of thermal decarbonation on stable isotope compositions of carbonates
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- Synchrotron X-ray diffraction study of the structure and dehydration behavior of todorokite
- Retrograde mineral reactions in saline fluid inclusions: The transformation ferropyrosmalite ↔ clinopyroxene
- The effect of ionizing radiation on uranophane
- Hydration, expansion, structure, and dynamics of layered double hydroxides
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- The amblygonite (LiAlPO4F)-montebrasite (LiAlPO4OH) solid solution: A combined powder and single-crystal neutron diffraction and solid-state 6Li MAS, CP MAS, and REDOR NMR study
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- Hydroxyl in clinopyroxene from the deep subducted crust: Evidence for H2O transport into the mantle
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Artikel in diesem Heft
- A molecular dynamics study of the behavior of sodium in low albite
- Observation and interpretation of paramagnetic defects in Brazilian and Central African carbonados
- Dissolution of gibbsite: Direct observations using fluid cell atomic force microscopy
- Polytypes and higher-order structures of antigorite: A TEM study
- An infrared spectroscopic study of the basic copper phosphate minerals: Cornetite, libethenite, and pseudomalachite
- Influence of F content on the composition of Al-rich synthetic phlogopite: Part I. New information on structure and phase-formation from 29Si, 1H, and 19F MAS NMR spectroscopies
- NMR evidence for formation of octahedral and tetrahedral Al and repolymerization of the Si network during dissolution of aluminosilicate glass and crystal
- Thermodynamic properties of hercynite (FeAl2O4) based on adiabatic calorimetry at low temperatures
- The formation of Sr silicates at low temperature and the solubility product of tobermorite-like Sr5Si6O16(OH)2 .5H2O
- Thermal equation of state of omphacite
- The effect of thermal decarbonation on stable isotope compositions of carbonates
- Synthetic MgAl2O4 (spinel) at high-pressure conditions (0.0001–30 GPa): A synchrotron X-ray powder diffraction study
- The stability of antigorite in the systems MgO-SiO2-H2O (MSH) and MgO-Al2O3-SiO2-H2O (MASH): The effects of Al3+ substitution on high-pressure stability
- The fusion curve of albite revisited and the compressibility of NaAlSi3O8 liquid with pressure
- Correction of secondary X-ray fluorescence near grain boundaries in electron microprobe analysis: Application to thermobarometry of spinel lherzolites
- An overgrowth model to explain multiple, dispersed high-Mn regions in the cores of garnet porphyroblasts
- Synchrotron X-ray diffraction study of the structure and dehydration behavior of todorokite
- Retrograde mineral reactions in saline fluid inclusions: The transformation ferropyrosmalite ↔ clinopyroxene
- The effect of ionizing radiation on uranophane
- Hydration, expansion, structure, and dynamics of layered double hydroxides
- Relict edenite in a garnet lherzolite from the Chinese Su-Lu UHP metamorphic terrane: Implications for metamorphic history
- Norrishite, K(Mn23+Li)Si4O10(O)2, an oxymica associated with sugilite from the Wessels Mine, South Africa: Crystal chemistry and 40Ar-39Ar dating
- The amblygonite (LiAlPO4F)-montebrasite (LiAlPO4OH) solid solution: A combined powder and single-crystal neutron diffraction and solid-state 6Li MAS, CP MAS, and REDOR NMR study
- An X-ray Rietveld, infrared, and Mössbauer spectral study of the NaMn(Fe1–xInx)2(PO4)3 alluaudite-type solid solution
- Gatelite-(Ce), a new REE-bearing mineral from Trimouns, French Pyrenees: Crystal structure and polysomatic relationships with epidote and törnebohmite-(Ce)
- Hydroxyl in clinopyroxene from the deep subducted crust: Evidence for H2O transport into the mantle
- A model for the structure of the hydrated aluminum phosphate, kingite determined by ab initio powder diffraction methods
- The crystal structure of synthetic autunite, Ca[(UO2)(PO4)]2(H2O)11