Structural Refinement of Olivine-Type LiMgAsO4

1992 ◽  
Vol 45 (9) ◽  
pp. 1355 ◽  
Author(s):  
J Barbier
Keyword(s):  
Neutron Diffraction ◽  
Structural Relationship ◽  
Structural Refinement ◽  
Space Group ◽  
Bond Lengths ◽  
Octahedral Sites ◽  
Powder Neutron Diffraction ◽  
Pnma Space Group ◽  
Average Bond

The refinement of the LiMgAsO4 structure by powder neutron diffraction confirms that it is isostructural with olivine. The structure is orthorhombic, Pnma space group, with a = 10.4183(15), b = 5.9660(8), c = 4.8692(5) �, and Z = 4. The lithium and magnesium atoms are fully ordered on the octahedral sites with average bond lengths (Li-O) = 2.187, (Mg-O) = 2.108 and (As-O) = 1.672 A. LiMgAsO4 is isostructural with LiMgPO4 but not with LiMgVO4. However, a close structural relationship exists between the arsenate and the vanadate involving similar cation arrays but different anion arrays.

The structure of Na2UCl6 and Li2UCl6 from multiphase powder neutron profile refinement

1983 ◽  
Vol 16 (2) ◽  
pp. 164-170 ◽  
Author(s):  
P. J. Bendall ◽  
A. N. Fitch ◽  
B. E. F. Fender
Keyword(s):  
Neutron Diffraction ◽  
Room Temperature ◽  
Lithium Ions ◽  
Two Phase ◽  
Relative Ease ◽  
Space Group ◽  
Octahedral Sites ◽  
Powder Neutron Diffraction ◽  
Phase Mixture ◽  
Profile Refinement

The structures of Na2UCl6 and Li2UCl6 have been determined by powder neutron diffraction at room temperature in the presence of NaCl and LiCl respectively as impurity. Na2UCl6crystallizes in space group P{\bar 3}m1, with a = 11 8062(9), c = 6.3243(2) Å, and Z = 3. The best description of Li2UCl6 was found in space group P63/mmc, a = 11.1915(5), c = 6.0356(1) Å, and Z = 3, with uranium and lithium ions disordered over the available octahedral sites. The results give the first illustration of the relative ease of analysing a two-phase mixture using a Rietveld profile program adapted to refine simultaneously more than one phase.

Crystallographic Studies of Nd3-xYxFe27.5TM1.5(0.6≤x≤2.4, TM=Ti, Mo) Compounds

2013 ◽  
Vol 785-786 ◽  
pp. 634-637
Author(s):  
Song Bai Han ◽  
Yun Tao Liu
Keyword(s):  
Neutron Diffraction ◽  
Type Structure ◽  
Space Group ◽  
Powder Neutron Diffraction ◽  
Thermodynamic Effects

Nd3-xYxFe27.5Ti1.5(0.6≤x≤2.4) and Nd3-x’Yx’Fe27.5Mo1.5(0.6≤x’≤2.4) alloys have been synthesized successfully and studied by means of powder neutron diffraction. The structural analyses indicate that the main phases in all cases crystallize in the monoclinic Nd3(Fe,Ti)29-type structure with a space group A2/m. Ti and Mo prefer to occupy 4g, 4i1 and 4i2 sites exclusively and the elemental site occupancies are dominated by the site sizes and thermodynamic effects.

The structures of some titanium-niobium oxides by powder neutron diffraction

1974 ◽  
Vol 338 (1614) ◽  
pp. 311-326 ◽  
Keyword(s):  
Neutron Diffraction ◽  
Profile Analysis ◽  
Detailed Examination ◽  
Ionic Model ◽  
Space Group ◽  
Cell Parameters ◽  
Powder Neutron Diffraction ◽  
Crystallographic Shear ◽  
Final Profile ◽  
Block Structures

The structures of TiNb 2 O 7 and ortho - Ti 2 Nb 10 O 29 have been examined at 4.2 K by total profile analysis of powder neutron diffraction data. The space group of TiNb 2 O 7 is A2/m and the cell parameters are a = 11.890(5), b = 3.804(2), c = 20.373(9) Å, ‡ β = 120.199 (3) deg. The final profile residual was 9.47%. The space group of ortho-Ti 2 Nb 10 O 29 is Amma and the cell parameters are a = 28.305(12), b = 3.780(2), c = 20.352(9) Å. A final profile residual of 10.62% was obtained. Substantial ordering of the cations among the different metal sites in these block structures was found, with titanium occupancy numbers varying from 14.0 to 64.5% for TiNb 2 O 7 and from 4.5 to 40.0% in ortho-Ti 2 Nb 10 O 29 . The values are consistent with site potentials obtained on an ionic model. The oxygen positions were determined with greater precision than in previous studies of block structures, affording a detailed examination of the dis­tortions around the crystallographic shear planes.

Isoselenocyanatoborate -Kristallstrukturen von (n-Bu4N)[BH(NCSe)3] und (Ph4P)[B3H7(NCSe)] / Isoselenocyanatoborates -Crystal Structures of (n-Bu4N)[BH(NCSe)3] and (Ph4P)[B3H7(NCSe)]

1998 ◽  
Vol 53 (3) ◽  
pp. 271-274 ◽  
Author(s):  
B. Steuer ◽  
W. Preetz
Keyword(s):  
Single Crystals ◽  
Crystal Structures ◽  
Elemental Selenium ◽  
Monoclinic Space Group ◽  
Triclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Bond Lengths ◽  
Structure Determinations ◽  
Average Bond

Abstract The treatment of [B6H6]2- with an excess of (SCN)2 in dichloromethane in the presence of solid KOH gives the hexaisoselenocyanatodiborate anion [B2(NCSe)6]2- as an intermediate (δ(11B) = -10.3 ppm), from which [BH(NCSe)3]- and elemental selenium are formed. The X-ray structure determinations on single crystals of (n-Bu4N)2[BH(NCSe)3] (1) (triclinic, space group Pi with a = 8.512(2), b = 10.885(3), c = 14.895(4) Å, α = 79.52(2), β = 74.86(2), γ = 86.768(2)°, Z = 2) and (Ph4P)[B3H7(NCSe)] (2) (monoclinic, space group C2, a = 7.686(5), b = 10.366(3), c = 17.533(3) A, β = 108.89°, Z = 4) show that the selenocyanate groups are coordinated exclusively via the N atoms with average bond lengths of B-N = 1.52, C-N = 1.15, C-Se = 1.75 A and angles N-C-Se = 179°, B-N-C = 168.7 - 176.8°. The N-B-N angles of 1 range from 107.5 to 109.5°.

scholarly journals Beiträge zur Strukturchemie phosphorhaltiger Ketten und Ringe, V [1] Die Molekül- und Kristallstruktur des 1.2.3.4-Tetra-tert-butyl-1.4-bis(trimethylsilyl)tetraphosphans, Me3Si-(t-BuP)4-SiMe3 / Structural Chemistry of Phosphorus-Containing Chains and Rings, V [1] Molecular and Crystal Structure of 1,2,3,4-Tetra-tert-butyl-1,4-bis(trimethylsilyl)tetraphosphane, (H3C)3Si-(t-BuP)4-Si(CH3)3

1982 ◽  
Vol 37 (5) ◽  
pp. 534-541 ◽  
Author(s):  
Karl-Friedrich Tebbe ◽  
Roland Fröhlich
Keyword(s):  
Crystal Structure ◽  
Structural Chemistry ◽  
Space Group ◽  
Short Contact ◽  
Bond Lengths ◽  
Tert Butyl ◽  
Phosphorus Containing ◽  
Central Bond ◽  
Inner Region ◽  
Average Bond

The compound 1,2,3,4-tetra-tert-butyl-1,4-bis(trimethylsilyl)tetraphosphane, Me3Si-(t-BuP)4-SiMe3, C22H54P4Si2, crystallizes monoclinically in the space group P21/n (No. 14) with a = 889.9 pm, b = 2292.8 pm, c = 1568.0 pm, β = 94.14° and Z = 4 formula units.The molecule forms a twisted Si-P4-Si-chain with two kinds of P-P-bonds. The atoms neighbouring the silicium atoms take part in bonds of length d̄(P-P) = 218.8 pm, whereas the central bond d̄(P-P) = 221.4 pm is much longer. A special feature of the structure is a short contact d̄(P-P) = 345.6 pm. Therefore, the inner region of the molecule has the shape of a nearly planar trapezium of the four phosphorus atoms. The periphery of the molecule is as expected. The average bond lengths are d̄(P-Si) = 228.5 pm, d̄(P-C) - 190.2 pm, d̄(Si-C) = 186.6 pm, d̄(C-C) = 151.8 pm and d̄(C-H) = 94 pm

Temperature dependence of the crystal structure of α-AgSCN by powder neutron diffraction

2007 ◽  
Vol 40 (6) ◽  
pp. 1039-1043 ◽  
Author(s):  
Darrick J. Williams ◽  
L. L. Daemen ◽  
S. C. Vogel ◽  
Th. Proffen
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Neutron Diffraction ◽  
Structural Changes ◽  
Rietveld Method ◽  
Tetrahedral Coordination ◽  
Bond Lengths ◽  
Powder Neutron Diffraction ◽  
Different Temperatures ◽  
Neutron Powder Diffractometer

A structural study of α-AgSCN was carried out using the neutron powder diffractometer HIPPO (high-pressure preferred orientation powder) at ten different temperatures between 25 and 275 K. The structure of α-AgSCN was refined using the Rietveld method and the symmetry elements for the material were found to be: space group No. 15,C2/c,a= 8.7210 (8) Å,b= 7.9318 (8) Å,c= 12.3329 (5) Å, β = 138.750 (3)°, volume = 562.497 (9) Å3andZ= 8. The Ag+cation has tetrahedral coordination and is surrounded by three –SCN thiocyanate ligands and one isothiocyanate –NCS ligand down to 25 K, with no structural changes. The bond lengths at 275 K are Ag—S1 = 2.749 (10), Ag—S2 = 2.995 (11), Ag—S3 = 2.411 (11), Ag—N = 2.150 (5), S—C = 1.783 (11) and C—N = 1.1447 (35) Å. The bond lengths at 25 K are Ag—S1 = 2.782 (5), Ag—S2 = 2.941 (5), Ag—S3 = 2.431 (5), Ag—N = 2.1526 (26), S—C = 1.749 (5) and C—N = 1.140 (2) Å.

A new LaCo0.71(1)V0.29(1)O2.97(3) perovskite containing vanadium in octahedral sites: synthesis and structural and magnetic characterization

2015 ◽  
Vol 44 (23) ◽  
pp. 10721-10727 ◽  
Author(s):  
V. C. Fuertes ◽  
M. C. Blanco ◽  
D. G. Franco ◽  
S. Ceppi ◽  
R. D. Sánchez ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Characterization ◽  
Octahedral Sites ◽  
Powder Neutron Diffraction

Powder neutron diffraction, Co-Kβ XES spectra and a polyhedral view of the orthorhombic LaCo0.71(1)V0.29(1)O2.97(3) perovskite.

Crystal structure of Mo-substituted lanthanum tungstate La5.4W1−y Mo y O12−δ (0 ≤ y ≤ 0.2) studied by X-ray and neutron diffraction

2019 ◽  
Vol 52 (5) ◽  
pp. 1043-1053 ◽  
Author(s):  
Andrea Fantin ◽  
Tobias Scherb ◽  
Janka Seeger ◽  
Gerhard Schumacher ◽  
Uta Gerhards ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Neutron Diffraction ◽  
Structural Model ◽  
Scattering Length ◽  
Pechini Method ◽  
Oxygen Deficiency ◽  
Space Group ◽  
X Ray ◽  
Bond Lengths ◽  
The Face

A determination of the detailed crystal structure of an Mo-substituted lanthanum tungstate series, La6−x W1−y Mo y O12−δ (0 ≤ y ≤ 0.2, δ is the oxygen deficiency), is presented. Material of composition La5.4W0.8Mo0.2O12−δ (y = 0.2) produced by the citrate-complexation route based on the Pechini method was investigated by high-resolution X-ray diffraction and neutron diffraction in the temperature range 10 ≤ T ≤ 298 K. The results are compared with a non-substituted material La5.4WO12−δ. A structural model established earlier for lanthanum tungstates and Re-substituted lanthanum tungstates is confirmed, according to which the Wyckoff site shared by La and W is split with half site occupancies (Fm\bar 3m space group, 48h site) and also accommodates Mo atoms. Substitution of W by up to 20 mol% Mo does not change the face-centred cubic lattice: Mo atoms substitute W statistically on both 4a and 48h Wyckoff sites of the crystal structure, which is described by the Fm\bar 3m space group. These results were obtained from the combination of the average neutron-scattering length and average X-ray scattering power procedures with electron-probe micro-analysis. The temperature dependence of bond lengths in dry and wet (D2O) conditions shows that vacant oxygen sites are located on the 32f Wyckoff sites also in Mo-substituted lanthanum tungstates, and that the bond lengths between La on 4b and O on 32f increase with increasing pO2 and pD2O, reflecting the filling of oxygen vacancies and the increase in coordination of La on 4b.

The Crystal Structure of Potassium Nickel Arsenate; KNiAsO4

1988 ◽  
Vol 43 (8) ◽  
pp. 1053-1055 ◽  
Author(s):  
A. M. Buckley ◽  
S. T. Bramwell ◽  
P. Day ◽  
W. T. A. Harrison
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Neutron Diffraction ◽  
Unit Cell ◽  
Hexagonal Cell ◽  
Space Group ◽  
Powder Neutron Diffraction

AbstractThe crystal structure of potassium nickel arsenate. KNiAsO4 has been determined by high resolution powder neutron diffraction at 30 K. The unit cell of KNiAsO4 is rhombohedral. space group R3̄, with hexagonal cell constants, a = 4.97208(2) (Å). c = 28.52606(10) (Å). The compound is isomorphous with NaNiAsO4.

The crystal structure of KCaF3 at 4.2 and 300 K: A re-evaluation using high-resolution powder neutron diffraction

2005 ◽  
Vol 20 (1) ◽  
pp. 7-13 ◽  
Author(s):  
K. S. Knight ◽  
C. N. W. Darlington ◽  
I. G. Wood
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Neutron Diffraction ◽  
Perovskite Phase ◽  
Lattice Parameters ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Powder Neutron Diffraction

The crystal structure of the perovskite phase KCaF3 has been redetermined at 4.2 and 300 K using powder neutron diffraction collected at the highest resolution. At both temperatures the phase was found to be orthorhombic in space group Pnma, with lattice parameters a=0.622 879(5) nm, b=0.870 031(7) nm, c=0.611 210(5) nm at 4.2 K, and a=0.621 488(6) nm, b=0.876 360(8) nm, c=0.616 481(6) nm at 300 K. The CaF6 octahedron is regular at both temperatures with octahedral rotations of 9.6° and 13.2° for the in-phase and anti-phase tilts, respectively, at 4.2 K. No evidence was found to support the recent revision of the space group from Pnma to the monoclinic space group B21∕m.

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