Towards a more reliable symmetry determination from powder diffraction: a redetermination of the low-temperature structure of 4-methylpyridine-N-oxide

2009 ◽  
Vol 65 (6) ◽  
pp. 784-786 ◽  
Author(s):  
Lukáš Palatinus ◽  
Françoise Damay
Keyword(s):  
Low Temperature ◽  
Powder Diffraction ◽  
Tunneling Spectroscopy ◽  
Temperature Structure ◽  
Determination Method ◽  
Neutron Data ◽  
Acta Cryst ◽  
Space Group ◽  
X Ray ◽  
New Space

The low-temperature structure of 4-methylpyridine-N-oxide was previously determined in symmetry P41 [Damay et al. (2006), Acta Cryst. B62, 627–633]. Using a recently published symmetry-determination method it was found that the true symmetry of the structure is P41212. The structure was refined in the new space group using X-ray and neutron data. The previously published structure is close to the newly refined structure, but the new structure is in agreement with the results of rotational tunneling spectroscopy, and, in contrast to the structure in symmetry P41, does not require a twofold degeneracy of the tunneling bands.

Crystal structures of room- and low-temperature phases in oxyfluoride (NH4)2KWO3F3

2007 ◽  
Vol 22 (3) ◽  
pp. 227-230 ◽  
Author(s):  
M. S. Molokeev ◽  
A. D. Vasiliev ◽  
A. G. Kocharova
Keyword(s):  
Low Temperature ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Room Temperature ◽  
Monoclinic Phase ◽  
Temperature Structure ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray

Crystal structures of (NH4)2KWO3F3 at 298 K and 113 K were solved from X-ray powder diffraction data and refined by the Rietveld technique. The compound is isostructural with elpasolite K2NaAlF6 at room temperature with space group Fm-3m, a=8.95850(5) Å, V=718.961(7) Å3, Z=4, Dx=3.363 g/cm3, and MW=364.02. The structure was refined over 18 parameters to Rwp=12.6%, Rp=10.9%, Rexp=5.03%, and RB=3.27% from 40 independent reflections. (NH4)2KWO3F3 was transformed upon cooling to a ferroelastic monoclinic phase with space group P21/n, a′=6.3072(3) Å, b′=6.3028(3) Å, c′=8.9882(3) Å, β′=90.242(2)°, V=357.30(3) Å3, Z=2, and Dx=3.383 g/cm3. The low-temperature structure at 113 K was refined over 28 parameters to Rwp=20.9%, Rp=21.3%, Rexp=12.5%, and RB=6.93% from 453 independent reflections.

Crystal data of the low-temperature solid form of 2-methyl-2-nitro-propanol(MNP)

1994 ◽  
Vol 9 (2) ◽  
pp. 84-86 ◽  
Author(s):  
J. Ll. Tamarit ◽  
N. B. Chanh ◽  
P. Négrier ◽  
D. O. López ◽  
M. Barrio ◽  
...  
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray ◽  
Type Space ◽  
Solid Form

By means of X-ray single crystal Weissenberg photographs, the crystal of the low-temperature solid form of 2-methyl-2-nitro-propanol, (CH3)2C(NO2)(CH2OH), has been determined and found to be of the monoclinic type, space group P21/c. The cell constants were refined from X-ray powder diffraction data: a=6.195(3) Å, b=19.116(7) Å, c=16.598(7) Å, and β = 90.12(2)° with Z = 12. The indexed pattern at 293 K is given.

scholarly journals Evidence for differentiation in the iron-helicoidal chain in GdFe3(BO3)4

2005 ◽  
Vol 61 (5) ◽  
pp. 481-485 ◽  
Author(s):  
S. A. Klimin ◽  
D. Fausti ◽  
A. Meetsma ◽  
L. N. Bezmaternykh ◽  
P. H. M. van Loosdrecht ◽  
...  
Keyword(s):  
Low Temperature ◽  
Room Temperature ◽  
Structural Phase ◽  
Structure Study ◽  
Temperature Structure ◽  
Space Group ◽  
X Ray ◽  
First Order ◽  
New Perspective ◽  
Insight Into

A single-crystal X-ray structure study of gadolinium triiron tetraborate, GdFe_3(BO_3)_4, at room temperature and at 90 K is reported. At room temperature GdFe_3(BO_3)_4 crystallizes in a trigonal space group, R32 (No. 155), the same as found for other members of the iron borate family RFe_3(BO_3)_4. At 90 K the structure of GdFe_3(BO_3)_4 transforms to the space group P3_{1}21 (No. 152). The low-temperature structure determination gives new insight into the weakly first-order structural phase transition at 156 K and into the related Raman phonon anomalies. The presence of two inequivalent iron chains in the low-temperature structure provides a new perspective on the interpretation of the low-temperature magnetic properties.

Powder diffraction data and Rietveld refinement of metastable t-ZrO2 at low temperature

1997 ◽  
Vol 12 (2) ◽  
pp. 96-98 ◽  
Author(s):  
J. Málek ◽  
L. Beneš ◽  
T. Mitsuhashi
Keyword(s):  
Low Temperature ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

Indexed X-ray powder diffraction data are reported for the low temperature tetragonal ZrO2 obtained by crystallization of zirconia gel. The structure was refined by the Rietveld technique on the basis of space group P42/nmc. Refined unit cell dimensions are a = 3.5984(5) Å, c = 5.152(1) Å, V = 66.71 Å3, Dx=6.135 g/cm3, F18=62 (0.012, 24), RP=8.99, Rwp=11.48, RB=3.13.

Low-Temperature Structure and Magnetic Properties of Tetraphenylarsonium Tetrachloronitridotechnetate(VI)

1996 ◽  
Vol 49 (5) ◽  
pp. 633 ◽  
Author(s):  
BN Figgis ◽  
PA Reynolds ◽  
FK Larsen ◽  
GA Williams ◽  
CD Delfs
Keyword(s):  
Crystal Structure ◽  
Magnetic Properties ◽  
Low Temperature ◽  
Neutron Diffraction ◽  
Single Crystals ◽  
Temperature Structure ◽  
X Ray Diffraction ◽  
Magnetic Susceptibilities ◽  
Space Group ◽  
X Ray

The crystal structure of [As(C6H5)4] [TcNCl4] was determined at 120 K by X-ray diffraction and at 28 K by neutron diffraction. The crystals are tetragonal, space group P4/n, with a 1260.4(3) and c 773.2(2) pm at 120 K. The [TcNCl4]-anion possesses exact C4v symmetry, with Tc≡N distances of 160.3(2) and 162.5(4)pm at 120 and 28 K respectively. Magnetic susceptibilities were measured on single crystals from 300 to 4.5 K. The results indicate a well behaved S ½ system following the Curie-Weiss law with θ -0.13 K

Structure of compounds E(SnMe3)4 (E = Si, Ge) as seen by high-resolution X-ray powder diffraction and solid-state NMR

2001 ◽  
Vol 58 (1) ◽  
pp. 52-61 ◽  
Author(s):  
Robert E. Dinnebier ◽  
Piotr Bernatowicz ◽  
Xavier Helluy ◽  
Angelika Sebald ◽  
Markus Wunschel ◽  
...  
Keyword(s):  
High Temperature ◽  
High Resolution ◽  
Low Temperature ◽  
Powder Diffraction ◽  
Variable Temperature ◽  
Lattice Parameter ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Space Group ◽  
X Ray

The compounds tetrakis(trimethylstannyl)germane, Ge(SnMe3)4 (1), and tetrakis(trimethylstannyl)silane, Si(SnMe3)4 (2), have crystal structures with the quasispherical molecules in a closed-packed stacking. At room temperature both structures have the space group P\bar 1 (Z = 2) with a = 9.94457 (5), b = 14.52927 (8), c = 9.16021 (5) Å, α = 90.53390 (30), β = 111.73080 (30), γ = 90.0049 (4)°, and V = 1229.414 (12) Å3 for (1) and a = 9.92009 (7), b = 14.51029 (11), c = 9.13585 (7) Å, α = 90.4769 (4), β = 111.6724 (4), γ = 89.9877 (6)°, and V = 1222.037 (16) Å3 for (2). The molecules are found to be ordered as a result of steric interactions between neighboring molecules, as shown by analyzing the distances between the atoms. Upon heating, both compounds undergo a first-order phase transition at temperatures Tc = 348 ± 5 K, as characterized by a relative jump of the lattice parameter of ∼16%. At 353 K, both structures have the space group P\bar 1 (Z = 4), with a = 14.2037 (2) Å, and V = 2865.52 (7) Å3 for (1) and a = 14.1346 (2) Å, and V = 2823.90 (7) Å3 for (2). Rietveld refinements were performed for the low-temperature phases measured at T = 295 K [R wp = 0.0844 for (1), R wp = 0.0940 for (2)] and for the high-temperature phases measured at T = 353 K [R wp = 0.0891 for (1), R wp = 0.0542 for (2)]. The combination of high-resolution X-ray powder diffraction measurements and variable-temperature magic-angle-spinning 13C, 29Si and 119Sn NMR experiments demonstrates low crystallographic and molecular (C 1) symmetries for the low-temperature phases of (1) and (2) at temperatures T < 348 ± 5 K and high crystallographic symmetry due to rotational disorder for the high-temperature phases at temperatures T > 348 ± 5 K.

scholarly journals Rietveld refinement of the low temperature crystal structures of Cs2XSi5O12 (X = Cu, Cd and Zn)

2021 ◽  
Vol 12 (1) ◽  
pp. 60-63
Author(s):  
Anthony Martin Thomas Bell
Keyword(s):  
High Temperature ◽  
Solid State ◽  
Low Temperature ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Low Temperatures ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray ◽  
Silicate Framework

The synthetic leucite silicate framework mineral analogues Cs2XSi5O12 (X = Cu, Cd, Zn) were prepared by high-temperature solid-state synthesis. The results of Rietveld refinement, using 18 keV synchrotron X-ray powder diffraction data collected at low temperatures (8K X = Cu, Zn; 10K X = Cd) show that the title compounds crystallize in the space group Pbca and are isostructural with the ambient temperature structures of these analogues. The structures consist of tetrahedrally coordinated SiO4 and XO4 sharing corners to form a partially substituted silicate framework. Extraframework Cs cations sit in channels in the framework. All atoms occupy the 8c general position for this space group. In these refined structures, silicon and X atoms are ordered onto separate tetrahedrally coordinated sites (T-sites).

Synchrotron X-Ray Powder Diffraction Studies of Structural Phase Transitions in Perovskite Oxides

2012 ◽  
Vol 65 (3) ◽  
pp. 229 ◽  
Author(s):  
Brendan J. Kennedy ◽  
Ilyas Qasim ◽  
Emily Reynolds ◽  
Teck-Yee Tan ◽  
Qingdi Zhou
Keyword(s):  
High Resolution ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Structural Parameters ◽  
Structural Phase ◽  
Temperature Structure ◽  
Space Group ◽  
X Ray ◽  
Pbnm Space Group ◽  
Perovskite Type

The utilization of the high resolution powder diffractometer at the Australian Synchrotron to obtain accurate and precise structures of some perovskite-type oxides is described. The structure of CdTiO3 has been studied from room temperature to 1000°C by high-resolution synchrotron X-ray powder diffraction. It was found that CdTiO3 remains orthorhombic in the Pbnm space group over the entire temperature range, with the expansion in the cell volume well fitted to the expression . The magnitudes of the TiO6 tilts are estimated from the refined structural parameters and these progressively reduce as the temperature is increased. The effect of Sr content on the room temperature structure of the double perovskites Ba2–xSrxInTaO6 is also described. At room temperature Ba2InTaO6 crystallizes in a cubic structure in space group . Doping with Sr results in tilting of the corner sharing octahedra with a concurrent lowering of symmetry with the sequence of structures being

Low-temperature structure of V6O13

2003 ◽  
Vol 59 (6) ◽  
pp. 747-752 ◽  
Author(s):  
Jonas Höwing ◽  
Torbjörn Gustafsson ◽  
John O. Thomas
Keyword(s):  
Low Temperature ◽  
Mirror Plane ◽  
Temperature Phase ◽  
Temperature Structure ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Acta Cryst ◽  
Lithium Polymer Batteries ◽  
Space Group ◽  
Dsc Measurements

The structure of the transition metal oxide V6O13, a potential cathode material in lithium-polymer batteries, has been studied at 95 K using single-crystal X-ray diffraction (XRD). A phase transition has been determined by differential scanning calorimetry (DSC) measurements to occur at 153 K, with a heat of transition of −1.98 kJ mol−1. In this low-temperature phase, the V and O atoms move by up to 0.21 Å out of the mirror plane they occupy in the room-temperature structure. It is concluded that the earlier reported space group P21/a [Kawada et al. (1978). Acta Cryst. B34, 1037–1039] is incorrect and that a more appropriate choice of space group is Pc.

Distorted chiolite crystal structures of α-Na5M3F14 (M=Cr,Fe,Ga) studied by X-ray powder diffraction

2003 ◽  
Vol 18 (2) ◽  
pp. 128-134 ◽  
Author(s):  
A. Le Bail ◽  
A.-M. Mercier
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Rietveld Refinements ◽  
Space Group ◽  
X Ray ◽  
Precise Characterization

The crystal structures of the chiolite-related room temperature phases α-Na5M3F14 (MIII=Cr,Fe,Ga) are determined. For all of them, the space group is P21/n, Z=2; a=10.5096(3) Å, b=7.2253(2) Å, c=7.2713(2) Å, β=90.6753(7)° (M=Cr); a=10.4342(7) Å, b=7.3418(6) Å, c=7.4023(6) Å, β=90.799(5)° (M=Fe), and a=10.4052(1) Å, b=7.2251(1) Å, c=7.2689(1), β=90.6640(4)° (M=Ga). Rietveld refinements produce final RF factors 0.036, 0.033, and 0.035, and RWP factors, 0.125, 0.116, and 0.096, for MIII=Cr, Fe, and Ga, respectively. The MF6 polyhedra in the defective isolated perovskite-like layers deviate very few from perfect octahedra. Subtle octahedra tiltings lead to the symmetry decrease from the P4/mnc space group adopted by the Na5Al3F14 chiolite aristotype to the P21/n space group adopted by the title series. Facile twinning precluded till now the precise characterization of these compounds.

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