Crystal structures of rare earth elements rich apatite analogues

1990 ◽  
Vol 191 (3-4) ◽  
Author(s):  
Nicoline Kalsbeek ◽  
Sine Larsen ◽  
Jørn G. Rønsbo
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
Hexagonal System ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions

AbstractThe crystal structures have been determined for britholite-(Ce) and lessingite-(Ce) from the type localities and a third sample (‘min X’) showing chemical similarities to both britholite-(Ce) and lessingite-(Ce). This sample is from the Ilímaussaq intrusion in Greenland. They are rare earth elements (REE) rich apatite analogues. Based on the X-ray diffraction results they were assigned to the hexagonal system with cell dimensions slightly larger than those of apatite. The three structures have been refined in the space group

scholarly journals Hydroflux syntheses and crystal structures of hydrogarnets Ba3[RE(OH)6]2 (RE = Sc, Y, Ho–Lu)

2020 ◽  
Vol 75 (11) ◽  
pp. 951-957
Author(s):  
Ralf Albrecht ◽  
Florian Graßme ◽  
Thomas Doert ◽  
Michael Ruck
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Single Crystal ◽  
Crystal Structures ◽  
Crystal Structure Data ◽  
X Ray Diffraction ◽  
Interatomic Distances ◽  
Space Group ◽  
X Ray ◽  
Rhombic Dodecahedra

AbstractColorless crystals of the barium rare earth hydrogarnets Ba3[RE(OH)6]2 (RE = Sc, Y, Ho–Lu) were synthesized under hydroflux conditions with KOH at about T = 200 °C starting from the respective RE2O3 and Ba (NO3)2. Single-crystal X-ray diffraction analysis on these distorted rhombic dodecahedra revealed the cubic space group Ia$‾{3}$d (no. 230). The crystal structures of the hydrogarnets Ba3[RE(OH)6]2 are discussed and compared with those of other hydrogarnets. The occurrence of additional reflections, which do not fulfill the reflection conditions of Ia$‾{3}$d, is analyzed and described by Renninger or λ/2 effects. A correlation is established between the space group adopted by a hydrogarnet and characteristic interatomic distances. In addition, single-crystal structure data of the strontium indium hydrogarnet Sr3[In(OH)6]2 are provided.

The phase transitions and crystal structures of Ba3 RM 2O7.5 complex oxides (R = rare-earth elements, M = Al, Ga)

1999 ◽  
Vol 55 (5) ◽  
pp. 828-839 ◽  
Author(s):  
A. M. Abakumov ◽  
R. V. Shpanchenko ◽  
O. I. Lebedev ◽  
G. Van Tendeloo ◽  
S. Amelinckx ◽  
...  
Keyword(s):  
Phase Transition ◽  
Rare Earth ◽  
High Temperature ◽  
Rare Earth Elements ◽  
Complex Oxides ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Disorder Phase Transition

The structures of α-Ba3 RAl2O7.5 and β-Ba3 RM 2O7.5 complex oxides (R = rare-earth elements, M = Al, Ga) have been studied by a combination of X-ray diffraction, electron diffraction (ED) and high-resolution electron microscopy (HREM). The α and β forms have cell parameters related to the perovskite subcell: a = 2a per, b = a per(2)1/2, c = 3a per(2)1/2, however, the α form has an orthorhombic unit cell whereas the β form adopts monoclinic symmetry. The crystal structure of monoclinic Ba3ErGa2O7.5 was refined from X-ray powder data (space group P2/c, a = 7.93617 (9), b = 5.96390 (7), c = 18.4416 (2) Å, β = 91.325 (1)°, R I = 0.023, R P = 0.053), the structure of the α form (space group Cmc21) was deduced from ED and HREM data. The important feature of the α and β structures is the presence of slabs containing strings of vertex-sharing tetrahedral Al2O7 pairs. Two almost equivalent oxygen positions within the strings can be occupied either in an ordered manner leading to the low-temperature β phase or randomly resulting in the high-temperature α structure. The critical temperature of this order–disorder phase transition was determined by high-temperature X-ray diffraction and by differential thermal analysis (DTA). In situ ED and HREM observations of the second-order phase transition confirmed the symmetry changes and revealed numerous defects (twins and antiphase boundaries) formed during the phase transformation.

Kristallstrukturen, Schwingungsspektren und Normalkoordinatenanalyse von cis-[ReCl4X2]2-, X = NCS, NCSe / Crystal Structures, Vibrational Spectra and Normal Coordinate Analysis of cis-[ReCl4X2]2-, X = NCS, NCSe

1998 ◽  
Vol 53 (11) ◽  
pp. 1329-1334 ◽  
Author(s):  
L. Homolya ◽  
S. Strueß ◽  
W. Preetz
Keyword(s):  
Crystal Structures ◽  
Normal Coordinate Analysis ◽  
X Ray Diffraction ◽  
Normal Coordinate ◽  
Triclinic Space Group ◽  
Valence Force ◽  
Space Group ◽  
X Ray ◽  
Valence Force Field ◽  
Ir And Raman

The crystal structures of cis-(n-Bu4N)2[ReCl4(NCS)2] (triclinic, space group P1̅, a = 11,245( 1), b = 20.174(3), c = 21.320(8) Å, a =109.06(2), β = 96.46(2), γ = 98.22(5)°, Z = 4) and cis-(Ph4P)2[ReCl4(NCSe)2]·2CH2Cl2 (triclinic, space group P1̅, a = 10.341(2), b = 13.436(3), c = 19.616(4) Å, α = 92.70(2), β = 92.02(2), γ = 89.99( 1)°, Z= 2) have been determined by single crystal X-ray diffraction analysis. Both ambidentate ligands NCS and NCSe are bonded via the N atom. Using the molecular parameters of the X-ray determinations the low temperature (10 K) IR and Raman spectra of the (n-Bu4N) salts have been assigned by normal coordinate analysis based on a modified valence force field. The valence force constants fd(ReN) are 1,78(NCS) and 1,79(NCSe) mdyn/ Å.

Structure Maps and Phase Stability in AlTi3 Alloyed with Rare-Earth Elements

1988 ◽  
Vol 133 ◽  
Author(s):  
C. T. Liu ◽  
J. A. Horton ◽  
D. G. Petitifor
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Rare Earth Elements ◽  
Solubility Limit ◽  
Size Factor ◽  
X Ray Diffraction ◽  
Atomic Size ◽  
X Ray ◽  
Dependent Parameter ◽  
Rare Earth Additions

ABSTRACTRare-earth elements including Y, Er and Sc were added to AlTi3 for stabilizing the Ll2 ordered crystal structure, as predicted by the AB3 structure map. The crystal structure and phase composition in the AlTi3 alloys were studied by electron microprobe analysis, X-ray diffraction and TEM. The solubility limit of the rare-earth elements were determined and correlated with the atomic size factor. The results obtained so far indicate that rare-earth additions are unable to change the crystal structure of AlTi3 from DO19 to Ll2. The inability to stabilize the Ll2 structure demonstrates the need to characterize the structure map domains with a further period-dependent parameter.

Powder X-Ray Diffraction Data for Ca2Bi2O5and C4Bi6O13

1992 ◽  
Vol 7 (2) ◽  
pp. 109-111 ◽  
Author(s):  
C.J. Rawn ◽  
R.S. Roth ◽  
H.F. McMurdie
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Neutron Powder Diffraction ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions ◽  
Powder Samples ◽  
Orthorhombic Cell ◽  
Unit Cell Dimensions

AbstractSingle crystals and powder samples of Ca2Bi5O5and Ca4Bi6O13have been synthesized and studied using single crystal X-ray diffraction as well as X-ray and neutron powder diffraction. Unit cell dimensions were calculated using a least squares analysis that refined to a δ2θof no more than 0.03°. A triclinic cell was found with space group , a = 10.1222(7), b = 10.1466(6), c = 10.4833(7) Å. α= 116.912(5), β= 107.135(6) and γ= 92.939(6)°, Z = 6 for the Ca2Bi2O5compound. An orthorhombic cell was found with space group C2mm, a = 17.3795(5), b = 5.9419(2) and c = 7.2306(2) Å, Z = 2 for the Ca4Bi6O13compound.

Die neuen Oxoarsenate(III) AAsO2 (A = Na, K, Rb) und Cs3As5O9. Darstellung, Kristallstrukturen und Raman-Spektren / The New Oxoarsenates(III) AAsO2 (A = Na, K, Rb) and Cs3As5O9. Synthesis, Crystal Structures and Raman Spectra

2003 ◽  
Vol 58 (7) ◽  
pp. 620-626 ◽  
Author(s):  
Franziska Emmerling ◽  
Caroline Röhr
Keyword(s):  
Crystal Structures ◽  
Metal Content ◽  
Alkali Metals ◽  
Alkaline Metal ◽  
Tetrahedral Coordination ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Metal Arsenates

The new alkaline metal arsenates(III) were synthesized at a temperature of 500 °C via reaction of stoichiometric mixtures of the elemental alkali metals A and As2O3. In the crystal structures of the four title compounds, which have been determined by single crystal x-ray diffraction, the As(III) atoms are in ψ-tetrahedral coordination by oxygen exclusively. In NaAsO2 (orthorhombic, space group Pbcm, a = 1429.6(9), b = 677.3(3), c = 509.1(2) pm, Z = 8) and the compounds AAsO2 (A = K/Rb, orthorhombic, space group Pbcm, a = 715.1(2)/729.7(5), b =748.0(1)/775.2(5), c = 539.20(17)/541.1(3) pm, Z = 4) the AsO3 ψ-tetrahedra are condensed to form zig-zag chains [AsOO2/2]−. In the Cs phase Cs3As5O9 with a lower alkaline metal content (trigonal, space group P31m, a = 845.5(3), c = 602.6(2) pm, Z = 1) the two crystallographically independent ψ-tetrahedra AsO3/2 and AsOO2/2 are connected in a 2:3 ratio to give polar sheets [As5O9]3−.

The Constituents of Marine Sponges. IX New Norditerpenoids from Aplysilla pallida

1997 ◽  
Vol 50 (9) ◽  
pp. 903 ◽  
Author(s):  
Trevor W. Hambley ◽  
Walter C. Taylor ◽  
Stephen Toth
Keyword(s):  
Crystal Structures ◽  
Spectroscopic Studies ◽  
Marine Sponges ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray

Four novel norditerpenoids were isolated from a new encrusting sponge, conveniently labelled Aplysilla pallida. The structures of aplypallidenone (1), aplypallidoxone (2), aplypallidione (3) and aplypallidioxone (4) were elucidated by spectroscopic studies and the crystal structures of aplypallidenone and aplypallidoxone have been determined by X-ray diffraction methods. The structure of (1) was refined to a residual of 0·040 for 1665 independent observed reflections and the structure of (2) was refined to a residual of 0·031 for 1699 independent observed reflections. The crystals of (1) are orthorhombic, space group P212121, a 7·728(2), b 10·838(4), c 24·880(5) Å, Z 4. Those of (2) are monoclinic, space group C 2, a 23·927(7), b 6·674(2), c 14·033(3) Å, Z 4.

scholarly journals Darstellung und Struktur ternärer Silizide und Germanide des Lithiums mit den Seltenen Erden Y und Gd im Fe2P-Typ / Preparation and Crystal Structure of Ternary Silicides and Germanides of Lithium with the Rare-Earth-Metals Y and Gd in the Fe2P-Type Structure

1979 ◽  
Vol 34 (8) ◽  
pp. 1057-1058 ◽  
Author(s):  
Axel Czybulka ◽  
Günter Steinberg ◽  
Hans-Uwe Schuster
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Crystal Structures ◽  
Rare Earth Metals ◽  
Type Structure ◽  
Space Group ◽  
X Ray ◽  
P Type ◽  
Type Lattice ◽  
The Rare Earth

In the systems Li-M-X = (M = Y, Gd; X = Si, Ge) the compounds LiYSi, LiYGe and LiGdGe were prepared. Their crystal structures were determined by X-ray investigations. They crystallize hexagonally (space group P 6̄2m), and a C22-(Fe2P-type) lattice was found

scholarly journals The crystal structures of kidwellite and ‘laubmannite’, two complex fibrous iron phosphates

2004 ◽  
Vol 68 (1) ◽  
pp. 147-165 ◽  
Author(s):  
U. Kolitsch
Keyword(s):  
Crystal Structures ◽  
Metal Cation ◽  
Iron Phosphate ◽  
Group Symmetry ◽  
X Ray Diffraction ◽  
Narrow Channels ◽  
Iron Phosphates ◽  
Space Group ◽  
X Ray ◽  
Complex Crystal

AbstractThe previously unknown, complex crystal structures of two fibrous ferric iron phosphate minerals have been solved using single-crystal X-ray diffraction data. The structure of a slightly arsenatian kidwellite has been refined in space group P2/c (a = 20.117(4), b = 5.185(1), c = 13.978(3)Å, β = 107.07(3)°, V = 1393.8(5)Å3, Z = 2) to R1 = 5.21%; a revision of both space group symmetry and chemical formula is proposed. The idealized formula is Na(Fe3+,M)9+x(OH)11(H2O)3(PO4)6, where M = Fe3+, Cu2+ or other metal cation, and x ≈ 0.3. The structure of a slightly arsenatian ‘laubmannite’ (as defined by Moore, 1970) has been refined in space group Pbcm (a = 5.172(1), b = 13.999(3), c = 31.083(6)Å, V = 2250.5(8)Å3, Z = 4) to R1 = 3.14%. The revised, idealized formula is (Fe3+,Fe2+,M)8+x(OH,H2O)9(-H2O)2(PO4)5, where M = Fe3+, Cu2+ or other metal cation, and x ≈ 0.1. The framework structures of both minerals are similar. Dominant building units are dimers composed of face- and edge-sharing FeO6 octahedra. Whereas kidwellite contains an additional trimer built of three corner-sharing FeO6 octahedra, ‘laubmannite’ instead contains a dimer built of two corner-sharing FeO6 octahedra. Kidwellite contains only trivalent iron, while one of the Fe sites in ‘laubmannite’ is occupied by a mixture of Fe3+ and Fe2+ in a 1:1 ratio. In both structures, the FeO6-based building units are linked via corners to PO4 tetrahedra; the M sites are located in narrow channels and have very low occupancies (~2 to 7%) and strongly distorted [6]- or [5+1]-coordinations. Close structural relations between kidwellite and ‘laubmannite’, and other fibrous iron phosphates explain observations of epitaxial intergrowths of them.

Die Kristallstruktur von Methyltriphenylphosphoniumhexachlorotitanat [MePh3P]2TiCl6 / The Crystal Structure of Methyltriphenylphosphonium Hexachlorotitanate

1981 ◽  
Vol 36 (2) ◽  
pp. 135-137 ◽  
Author(s):  
Evamarie Hey ◽  
Ulrich Müller
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Unit Cell ◽  
Distorted Octahedron ◽  
Inversion Center ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions

The crystal structure of [MePh3P]2TiCl6 was determined from X-ray diffraction data and refined to a residual index of R = 0.065. It crystallizes in the space group P2i/n with two formula units per unit cell; the cell dimensions are a - 921, b = 1314, c = 1648 pm and y - 100.87°. The TiCl62- ion occupies an inversion center and has the shape of a slightly distorted octahedron with Ti-Cl distances between 233 and 235 pm.

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