Incorporation of Mg in phase Egg, AlSiO3OH: Toward a new polymorph of phase H, MgSiH2O4, a carrier of water in the deep mantle

2020 ◽  
Vol 105 (1) ◽  
pp. 132-135 ◽  
Author(s):  
Luca Bindi ◽  
Aleksandra Bendeliani ◽  
Andrey Bobrov ◽  
Ekaterina Matrosova ◽  
Tetsuo Irifune
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Lower Mantle ◽  
Water Cycle ◽  
Molecular Water ◽  
Hydroxyl Groups ◽  
X Ray Diffraction ◽  
Coordination Polyhedra ◽  
X Ray ◽  
Mg Substitution

Abstract The crystal structure and chemical composition of a crystal of Mg-bearing phase Egg with a general formula M1−x3+Mx2+SiO4H1+x (M3+ = Al, Cr; M2+ = Mg, Fe), where x = 0.35, produced by subsolidus reaction at 24 GPa and 1400 °C of components of subducted oceanic slabs (peridotite, basalt, and sediment), was analyzed by electron microprobe and single-crystal X-ray diffraction. Neglecting the enlarged unit cell and the consequent expansion of the coordination polyhedra (as expected for Mg substitution for Al), the compound was found to be topologically identical to phase Egg, AlSiO3OH, space group P21/n, with lattice parameters a = 7.2681(8), b = 4.3723(5), c = 7.1229(7) Å, β = 99.123(8)°, V = 223.49(4) Å3, and Z = 4. Bond-valence considerations lead to hypothesize the presence of hydroxyl groups only, thereby excluding the presence of the molecular water that would be present in the hypothetical end-member MgSiO3·H2O. We thus demonstrate that phase Egg, considered as one of the main players in the water cycle of the mantle, can incorporate large amounts of Mg in its structure and that there exists a solid solution with a new hypothetical MgSiH2O4 end-member, according to the substitution Al3+ ↔ Mg2+ + H+. The new hypothetical MgSiH2O4 end-member would be a polymorph of phase H, a leading candidate for delivering significant water into the deepest part of the lower mantle.

Structural and phase equilibria studies in the system Pt-Fe-Cu and the occurrence of tulameenite (Pt2FeCu)

1985 ◽  
Vol 49 (353) ◽  
pp. 547-554 ◽  
Author(s):  
M. Shahmiri ◽  
S. Murphy ◽  
D. J. Vaughan
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Critical Temperature ◽  
Grain Boundary ◽  
Phase Region ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Slow Cooling ◽  
X Ray ◽  
Diffraction Patterns

AbstractThe crystal structure and compositional limits of the ternary compound Pt2FeCu (tulameenite), formed either by quenching from above the critical temperature of 1178°C or by slow cooling, have been investigated using X-ray diffraction, transmission electron microscopy, differential thermal analysis and electron probe microanalysis.The crystal structure of Pt2FeCu, established using electron density maps constructed from the measured and calculated intensities of X-ray diffraction patterns of powdered specimens, has the (000) and (½½0) lattice sites occupied by Pt atoms and the (½0½) and (0½½) sites occupied by either Cu or Fe atoms in a random manner. The resulting face-centred tetragonal structure undergoes a disordering transformation at the critical temperature to a postulated non-quenchable face-centred cubic structure. Stresses on quenching, arising from the ordering reaction, are relieved by twinning along {101} planes or by recrystallization along with deformation twinning; always involving grain boundary fracturing.Phase relations in the system Pt-Fe-Cu have been investigated through the construction of isothermal sections at 1000 and 600°C. At 1000°C there is an extensive single phase region of solid solution around Pt2FeCu and extending to the binary composition PtFe. At 600°C the composition Pt2FeCu lies just outside this now reduced area of solid solution in a two-phase field. Comparison of the experimental results with data for tulameenite suggests that some observed compositions may be metastably preserved. The occurrence of fine veinlets of silicate or other gangue minerals in tulameenite is suggested to result from grain boundary fracturing on cooling below the critical temperature of 1178°C and to be evidence of a magmatic origin.

Structure and Thermal Expansion Behavior of Dy2-xGdxMo4O15 Solid Solution

2008 ◽  
Vol 368-372 ◽  
pp. 1665-1667
Author(s):  
M.M. Wu ◽  
X.L. Xiao ◽  
Y.Z. Cheng ◽  
J. Peng ◽  
D.F. Chen ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Thermal Expansion ◽  
Monoclinic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Expansion Coefficients ◽  
Cell Volumes

A new series of solid solutions Dy2-xGdxMo4O15 (x = 0.0-0.9) were prepared. These compounds all crystallize in monoclinic structure with space group P21/c. The lattice parameters a, b, c and unit cell volumes V increase almost linearly with increasing gadolinium content. The intrinsic thermal expansion coefficients of Dy2-xGdxMo4O15 (x = 0.0 and 0.25) were obtained in the temperature range of 25 to 500°C with high-temperature X-ray diffraction. The correlation between thermal expansion and crystal structure was discussed.

Singly Charged λ6Si-Silicate Anions with an SiF5C Skeleton: Syntheses and Crystal Structure Analyses of the Ionic Hexacoordinate Silicon Compounds [Me3NH][F5SiCH2NMe2H]·H2O and [Me3NH][F5SiCH2NMe2H]·H2O

2000 ◽  
Vol 55 (1) ◽  
pp. 60-64
Author(s):  
Melanie Pülm ◽  
Joachim Becht ◽  
Reinhold Tacke
Keyword(s):  
Crystal Structure ◽  
Lewis Acids ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Coordination Polyhedra ◽  
Silicon Compounds ◽  
X Ray ◽  
Distorted Octahedra ◽  
Singly Charged ◽  
Crystalline Hydrates

The zwitterionic λ5Si-tetrafluorosilicates F4SiCH2NMe2H (1) and F4SiCH2NMe3 (2) behave as Lewis acids and react with [Me3NH]F (molar ratio 1:1) in aqueous solution to yield the ionic λ6Si-pentafluorosilicates [Me3NH][F5SiCH2NMe2H] (3) and [Me3NH][F5SiCH2NMe3] (4), respectively. These hexacoordinate silicon compounds contain singly charged λ6Si-silicate anions ([F5SiCH2NMe2H]- , [F5SiCH2NMe3]- ) with an SiF5C skeleton. Compounds 3 and 4 were isolated as the crystalline hydrates 3·H2O (yield 80%) and 4·H2O (yield 82%) which were structurally characterized by single-crystal X-ray diffraction. The Si-coordination polyhedra in the crystals of 3·H2O and 4·H2O are slightly distorted octahedra

scholarly journals Diterbium heptanickel: a crystal structure redetermination

2014 ◽  
Vol 70 (8) ◽  
pp. i42-i42
Author(s):  
Volodymyr Levytskyy ◽  
Volodymyr Babizhetskyy ◽  
Bohdan Kotur ◽  
Volodymyr Smetana
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Title Compound ◽  
Stoichiometric Composition ◽  
Structure Type ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
Coordination Polyhedra ◽  
X Ray ◽  
Anisotropic Displacement Parameters

The crystal structure of the title compound, Tb2Ni7, was redetermined from single-crystal X-ray diffraction data. In comparison with previous studies based on powder X-ray diffraction data [Lemaireet al.(1967).C. R. Acad. Sci. Ser. B,265, 1280–1282; Lemaire & Paccard (1969).Bull. Soc. Fr. Mineral. Cristallogr.92, 9–16; Buschow & van der Goot (1970).J. Less-Common Met.22, 419–428], the present redetermination affords refined coordinates and anisotropic displacement parameters for all atoms. A partial occupation for one Tb atom results in the non-stoichiometric composition Tb1.962 (4)Ni7. The title compound adopts the Ce2Ni7structure type and can also be derived from the CaCu5structure type as an intergrowth structure. The asymmetric unit contains two Tb sites (both site symmetries 3m.) and five Ni sites (.m.,mm2, 3m., 3m., -3m.). The two different coordination polyhedra of Tb are a Frank–Kasper polyhedron formed by four Tb and 12 Ni atoms and a pseudo Frank–Kasper polyhedron formed by two Tb and 18 Ni atoms. The four different coordination polyhedra of Ni are Frank–Kasper icosahedra formed by five Tb and seven Ni atoms, four Tb and eight Ni atoms, three Tb and nine Ni atoms, and six Tb and six Ni atoms, respectively.

The crystal structure of seeligerite, Pb3IO4Cl3, a rare Pb-I-oxychloride from the San Rafael mine, Sierra Gorda, Chile

2008 ◽  
Vol 72 (3) ◽  
pp. 771-783 ◽  
Author(s):  
L. Bindi ◽  
M. D. Welch ◽  
P. Bonazzi ◽  
G. Pratesi ◽  
S. Menchetti
Keyword(s):  
Crystal Structure ◽  
Lone Pair ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Coordination Polyhedra ◽  
X Ray ◽  
Cell Parameters ◽  
Square Planar ◽  
San Rafael ◽  
Cl Atoms

AbstractThe crystal structure of seeligerite, Pb3IO4Cl3, from the San Rafael mine, Sierra Gorda, Chile, was solved in the space group Cmm2, and refined to R = 3.07%. The unit-cell parameters are: a = 7.971(2), b = 7.976(2), c = 27.341(5) Å, V = 1738.3(6) Å3 and Z = 8. The crystal structure consists of a stacking sequence along [001] of square-net layers of O atoms and square-net layers of Cl atoms with Pb+ and I+ cations located in the voids of the packing. As is typical of cations with a stereoactive lone-pair of electrons, Pb2+ and I5+ adopt strongly-asymmetrical configurations. Pb2+ cations occur in a variety of coordination polyhedra, ranging from anticubes and monocapped anticubes to pyramidal ‘one-sided’ coordinations. I5+ is coordinated by a square of four oxygen atoms: I1 and I3 exhibit a ‘one-sided’ coordination, whereas I2 has square-planar coordination.The TEM investigation has revealed additional superlattice reflections (which were not registered by X-ray diffraction (XRD)) in the hk0 diffraction pattern of seeligerite based upon a 0.158 Å-1 square net, which can be interpreted as arising from a 20-cation super-sheet motif (12.6 Å x 12.6 Å), likely related to a further level of Pb-I order superimposed upon the 8-site motif identified by XRD.

scholarly journals Crystal structure of 5-[(benzoyloxy)methyl]-5,6-dihydroxy-4-oxocyclohex-2-en-1-yl benzoate

2020 ◽  
Vol 76 (7) ◽  
pp. 1096-1100
Author(s):  
Theerachart Leepasert ◽  
Patchreenart Saparpakorn ◽  
Kittipong Chainok ◽  
Tanwawan Duangthongyou
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Single Crystal ◽  
Natural Product ◽  
Dihedral Angle ◽  
Absolute Configuration ◽  
Hydroxyl Groups ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ring Form

The crystal structure of the natural product zeylenone, C21H18O7, was confirmed by single-crystal X-ray diffraction. The crystal structure has three chiral centers at positions C1, C5 and C6 of the cyclohexanone ring, but the absolute configuration could not be determined reliably. The methyl benzoate and benzoyloxy substituents at positions C1 and C5 of the cyclohexenone ring are on the same side of the ring with the dihedral angle between their mean planes being 16.25 (10)°. These rings are almost perpendicular to the cyclohexenone ring. The benzoate groups and two hydroxyl groups on the cyclohexenone ring form strong hydrogen bonds to consolidate the crystal structure. In addition, weak C—H...O hydrogen bonds also contribute to the packing of the structure.

Synthesis of Zn1–xMgxO and its structural characterization

2001 ◽  
Vol 16 (4) ◽  
pp. 903-906 ◽  
Author(s):  
M. S. Tomar ◽  
R. Melgarejo ◽  
P. S. Dobal ◽  
R. S. Katiyar
Keyword(s):  
Crystal Structure ◽  
Spin Coating ◽  
Optoelectronic Devices ◽  
Spectroscopic Studies ◽  
Structural Behavior ◽  
Material System ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Mg Substitution

Zn1–xMgxO is an important material for optoelectronic devices. We synthesized this material using a solution-based route. We investigated in detail the structural behavior of this material system using x-ray diffraction and Raman spectroscopy. Mg substitution up to x ≈ 0.10 does not change the crystal structure, as revealed by x-ray diffraction and Raman spectroscopic studies. This synthesis route is also suitable to prepare thin films by spin coating with the possibility of p and n doping.

Crystal structure of a synthetic aluminoan tantalian titanite: a reconnaissance study

2006 ◽  
Vol 70 (1) ◽  
pp. 115-121 ◽  
Author(s):  
R. P. Liferovich ◽  
R. H. Mitchell
Keyword(s):  
Crystal Structure ◽  
Structural Data ◽  
Rietveld Analysis ◽  
Synthetic Analogue ◽  
X Ray Diffraction ◽  
Coordination Polyhedra ◽  
X Ray ◽  
Ceramic Synthesis ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

AbstractA synthetic analogue, Ca(Ti0.6Al0.2Ta0.16Nb0.04)OSiO4, of an aluminoan tantalian titanite previously described from Craveggia pegmatite (Piemonte, Italy) has been prepared by a ceramic synthesis technique and its crystal structure determined by Rietveld analysis of the powder X-ray diffraction pattern. The synthetic Al-Ta-Nb-rich titanite adopts space group A2/a implying that substitutions at the single octahedral site destroy the coherence of the off-centering of octahedral chains in the titanite structure resulting in a P21/a → A2/a phase transition. Unit-cell dimensions obtained for the Al-Ta-Nb-rich titanite are: a = 7.0649(1) Å; b = 8.7187(1) Å; c = 6.5701(1) Å; β = 113.755(1)°, V = 370.41(1) Å3. The extensive replacement of Ti by Al, Ta and Nb results in a considerable decrease in the distortion of all coordination polyhedra in the structure of this titanite. These structural data suggest that a solid solution CaTi1-x(Alx/2 [Ta,Nb]x/2)OSiO4 (0 ≤ x ≤ 0.4) adopting the titanite structure might exist.

Preparation and Magnetic Properties of Nanocrystalline (Fe,Cr)-N

2012 ◽  
Vol 625 ◽  
pp. 222-225
Author(s):  
Wen Jiang Feng ◽  
Chuan Yin Wang ◽  
Hao Hua Zhang
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Magnetic Properties ◽  
Magnetic Moment ◽  
Single Phase ◽  
Nitrogen Atmosphere ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nano Crystalline ◽  
Intrinsic Magnetic Moment

The nano-crystalline (Fe,Cr)N was prepared as a single phase by milling Fe80Cr20 in a nitrogen atmosphere. Its crystal structure is determined to be the cubic rock salt-type CrN by X-ray diffraction measurements. The nano-crystalline is stable up to above 773 K and decomposes into (Fe,Cr)N and Fe-Cr solid solution. Due to the combination of Fe atoms and N ones, the intrinsic magnetic moment of Fe atoms is reduced, which is confirmed by our measurements.

Crystal structure of dicadmium(II) ethylenediphosphinetetraacetate octahydrate

1991 ◽  
Vol 56 (7) ◽  
pp. 1454-1460 ◽  
Author(s):  
Jaroslav Podlaha ◽  
Jana Podlahová
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Single Crystal ◽  
Diffraction Data ◽  
Title Compound ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Coordination Polyhedra ◽  
X Ray ◽  
Carboxylate Groups

The crystal structure of the title compound containing a phosphorus analogue of EDTA as the ligand was determined from single-crystal X-ray diffraction data and refined to R = 0.028 for 1 920 observed reflections. The crystals are monocyclic, space group P21/c,a = 8.6169(8), b = 16.0539(9), c = 8.2504(6)Å, β = 103.458(7)° and Z = 2. The structure is completely different from that of the nitrogen prototype, [CdEDTA]2-. It consists of double-stranded polymeric layers which are composed of metal coordination polyhedra linked by μ6-hexadentate ligands; the layers lie parallel to the bc plane and are joined along the a axis through hydrogen bonding donated by water molecules. Because of steric requirements of phosphorus, the coordination polyhedron around Cd is greatly distorted and can best be described as a 5 + 3 type. One P atom, two oxygen atoms from two monodentate carboxylate groups and two water molecules form an approximate trigonal bipyramid and further three more remote carboxylate oxygens complete the arrangement, resulting in an O7P distorted bicapped trigonal prism.

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