scholarly journals Synthesis and Crystal Structure of Nb0.84N

2011 ◽  
Vol 66 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Nancy Frenzel ◽  
Elisabeth Irran ◽  
Martin Lerch ◽  
Alexandra Buchsteiner
Keyword(s):  
Crystal Structure ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Close Packing ◽  
Powder Diffraction Data ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Layer Sequence ◽  
Neutron Powder Diffraction Data ◽  
Metal Layers

A new compound of the composition Nb0.84N was prepared by ammonolysis of NbO2 at 1100 °C. The crystal structure refinement was performed by the Rietveld method using X-ray and neutron powder diffraction data. Nb0.84N crystallizes in the trigonal space group R3m (no. 166) with the lattice parameters a = 298.5(2) and c = 2384.3(4) pm. The niobium atoms form a close packing with a layer sequence which can be described by the Jagodzinski symbol hhc. The nitrogen atoms fill all octahedral voids. Along [001] a sequence of two layers of trigonal NbN6 prisms and one layer of NbN6 octahedra is formed. The nitrogen positions are fully occupied, the niobium positions only partially. Nb0.84N is part of a family of crystal structures between the anti-NiAs and the NaCl type consisting of close-packed metal layers with varying stacking sequences

Rietveld Structure Refinement of Metastable Lithium Disilicate Using Synchrotron X-Ray Powder Diffraction Data From the Daresbury SRS 8.3 Diffractometer

1990 ◽  
Vol 5 (3) ◽  
pp. 137-143 ◽  
Author(s):  
R.I. Smith ◽  
A.R. West ◽  
I. Abrahams ◽  
P.G. Bruce
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Powder Diffraction Data ◽  
X Ray ◽  
New Instrument ◽  
Diffraction Peaks

AbstractThe crystal structure of metastable Li2Si2O5, Fw = 150.05, has been refined by the Rietveld method using high resolution X-ray powder diffraction data recorded at the Daresbury Synchrotron Radiation Source on the new 8.3 diffractometer. Li2Si2O5, in keeping with many compounds of interest to the materials scientist, exhibits relatively broad diffraction peaks. It is important to establish the quality of crystal structure data that may be obtained from such materials on this new instrument. Various functions were used to model the peak shape from this instrument; a split-Pearson VII function appeared to be marginally superior to Pearson VII or Pseudo-Voigt functions. Refinement was carried out using the split-Pearson VII in the space group Pbcn (60) and terminated with a = 5.6871(6), b = 4.7846(5), c = 14.645(1) Å, V = 398.50 Å3, Z=4, Dc= 2.502 gcm−3, Rwp = 17.06, Rex = 14.48 and Χ2 = 1.39. The refined parameters are compared with those obtained from a previous single crystal X-ray determination.

Synthesis and crystal structure of Co2(OH)2CO3 by Rietveld method

2010 ◽  
Vol 25 (S1) ◽  
pp. S7-S10 ◽  
Author(s):  
Shunli Wang ◽  
Guanglie Lü ◽  
Weihua Tang
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Cobalt Hydroxide ◽  
Site Symmetry ◽  
Powder Diffraction Data ◽  
Monoclinic System ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Oxygen Atoms

A new cobalt hydroxide carbonate Co2(OH)2CO3 was successfully synthesized by a hydrothermal method. The compound is isomorphous with malachite [Cu2(OH)2CO3] and crystallizes in a monoclinic system [space group P21/a (No. 14); a=9.448(5) Å, b=12.186(9) Å, c=3.188(4) Å, β=98.593°, V=367.143(9) Å3, Z=4, and Dc=3.786(9) g/cm3]. Crystal structure of Co2(OH)2CO3 was refined by the Rietveld method with RP=4.3%, RWP=5.7%, Rexp=5.1%, RB=1.74%, and S=1.117 on the basis of the X-ray powder diffraction data. The crystal structure of Co2(OH)2CO3 obtained by the Rietveld refinement shows that all species Co2+, CO32−, and OH− ions occupy C1 site symmetry. Two crystallographically different Co2+ and OH− ions and one type CO32− ion exist in the lattice. Co(1) is coordinated to two oxygen atoms from CO32− ions and two OH− ions; Co(2) is coordinated to two oxygen atoms from CO32− ions and four OH− ions, thus forming a distorted octahedron with (4+2) coordination.

Synthesis and crystal structure of the pyrovanadate Na2ZnV2O7

2005 ◽  
Vol 20 (3) ◽  
pp. 189-192 ◽  
Author(s):  
Alexander P. Tyutyunnik ◽  
Vladimir G. Zubkov ◽  
Ludmila L. Surat ◽  
Boris V. Slobodin ◽  
Gunnar Svensson
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Neutron Powder Diffraction ◽  
Type Structure ◽  
Powder Diffraction Data ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Tetragonal Unit Cell

The compound Na2ZnV2O7 with an åkermanite-type structure has been synthesized. It has a tetragonal unit cell, a=8.2711(4), c=5.1132(2) Å, and crystallizes with P-421m symmetry, Z=2. Its crystal structure has been refined from a combination of X-ray and neutron powder diffraction data. The structure contains layers of corner-sharing VO4 and ZnO4 tetrahedra, the former in pairs forming pyrovanadate V2O7 units. The sodium atoms are positioned between the layers, with a distorted antiprismatic coordination of oxygen atoms.

scholarly journals Revision of the structure of Cs2CuSi5O12 leucite as orthorhombic Pbca

2010 ◽  
Vol 66 (1) ◽  
pp. 51-59 ◽  
Author(s):  
A. M. T. Bell ◽  
K. S. Knight ◽  
C. M. B. Henderson ◽  
A. N. Fitch
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Rietveld Method ◽  
Neutron Powder Diffraction ◽  
Cation Ordering ◽  
Powder Diffraction Data ◽  
Acta Cryst ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Leucite Structure

The crystal structure of a hydrothermally synthesized leucite analogue Cs2CuSi5O12 has been determined and refined using the Rietveld method from high-resolution synchrotron X-ray and neutron powder diffraction data. This structure is based on the topology and cation-ordering scheme of the Pbca leucite structure of Cs2CdSi5O12, and exhibits five ordered Si sites and one ordered Cu tetrahedrally coordinated (T) site. This structure for Cs2CuSi5O12 is topologically identical to other known leucite structures and is different from that originally proposed by Heinrich & Baerlocher [(1991), Acta Cryst. C47, 237–241] in the tetragonal space group P4_12_12. The crystal structure of a dry-synthesized leucite analogue Cs2CuSi5O12 has also been refined; this has the Ia\bar 3d cubic pollucite structure with disordered T sites.

scholarly journals Synthesis and crystal structure determination of the new olivine-type compound Mn2SnSe4

2019 ◽  
Vol 66 (1) ◽  
pp. 30
Author(s):  
C. Chacón ◽  
P. Delgado-Niño ◽  
G.E. Delgado
Keyword(s):  
Rietveld Method ◽  
Close Packing ◽  
Powder Diffraction Data ◽  
Unit Cell Parameters ◽  
Orthorhombic Space Group ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Cell Parameters ◽  
Olivine Structure

The Mn2SnSe4 compound was synthesized by the melt and annealing technique and its structure was refined by the Rietveld method using X-ray powder diffraction data. This compound crystallizes in the olivine-type structure with unit cell parameters a = 12.9028(2) Å, b = 7.9001(1) Å, c = 6.5015(1) Å, V = 662.72(2) Å3 in the orthorhombic space group Pnma (Nº 62). This olivine structure can be described from a hexagonal close-packing of selenium atoms where manganese atoms occupy ½ of the octahedral sites while thin atoms lay in ⅛ of the tetrahedra.

Structure refinement and superspace description of the system Bi2(n + 2)Mo n O6(n + 1) (n = 3, 4, 5 and 6)

2012 ◽  
Vol 68 (4) ◽  
pp. 323-340 ◽  
Author(s):  
P. J. Bereciartua ◽  
F. J. Zuñiga ◽  
J. M. Perez-Mato ◽  
V. Petříček ◽  
E. Vila ◽  
...  
Keyword(s):  
Rietveld Method ◽  
Structure Refinement ◽  
Neutron Powder Diffraction ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Cationic Distribution ◽  
The Family ◽  
Superspace Formalism ◽  
Superspace Description

The system Bi2(n + 2)Mo n O6(n + 1) is described within the superspace formalism. Two superspace models are proposed for the different members of this family, depending on the parity of the parameter n. The superspace model for the odd members is constructed through the embedding of the cationic distribution of the member with n = 3, and the modification of a superspace model previously proposed for the compound Bi2MoO6. However, this model cannot be applied to the even members of the family. Performing the appropriate transformations, a suitable superspace model for the even members is obtained. The atomic structure of the different compounds of the family have been refined through the Rietveld method combining synchrotron X-ray and neutron powder diffraction data.

Determination and Rietveld refinement of the crystal structure of Li0.50Ni0.25TiO(PO4) from powder X-ray and neutron diffraction

2002 ◽  
Vol 17 (4) ◽  
pp. 290-294 ◽  
Author(s):  
B. Manoun ◽  
A. El Jazouli ◽  
P. Gravereau ◽  
J. P. Chaminade ◽  
F. Bouree
Keyword(s):  
Crystal Structure ◽  
Neutron Diffraction ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Neutron Powder Diffraction ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Monoclinic Cell

The structure of the oxyphosphate Li0.50Ni0.25TiO(PO4) has been determined from conventional X-ray and neutron powder diffraction data. The parameters of the monoclinic cell (space group P21/c, Z=4), obtained from X-ray results, are: a=6.3954(6) Å, b=7.2599(6) Å, c=7.3700(5) Å, and β=90.266(6)°; those resulting from neutron study are: a=6.3906(7) Å, b=7.2568(7) Å, c=7.3673(9) Å, and β=90.234(7)°. Refinement by the Rietveld method using whole profile, leads to satisfactory reliability factors: cRwp=0.128, cRp=0.100, and RB=0.038 for X-ray and cRwp=0.110, cRp=0.120, and RB=0.060 for neutrons. The structure of Li0.50Ni0.25TiO(PO4) can be described as a TiOPO4 framework constituted by chains of tilted corner-sharing TiO6 octahedra running parallel to the c axis and cross linked by phosphate tetrahedra. In this framework, there are octahedral cavities occupied by Li and Ni atoms: Li occupies the totality of the 2a sites and Ni occupies statistically half of the 2b sites. Ti atoms are displaced from the center of octahedra units in alternating long (2.242 Å) and short (1.711 Å) Ti–O bonds along chains.

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