Spectroscopic confirmation of orientational disorder of the cyanide groups in sodium cyanide dihydrate, NaCN•2H2O

1981 ◽  
Vol 59 (8) ◽  
pp. 1267-1269 ◽  
Author(s):  
Michael Falk
Keyword(s):  
Diffraction Data ◽  
Sodium Cyanide ◽  
X Ray Diffraction ◽  
Orientational Disorder ◽  
X Ray ◽  
Normal Orientation ◽  
Doublet Band

Occurrence of orientational disorder involving the CN groups in NaCN•2H2O, suggested by van Rij and Britton on the basis of a refinement of X-ray diffraction data, has been confirmed by the doubling of CN stretching fundamentals. The ratios of doublet band areas are consistent with the energy of the orientation [Formula: see text] being higher than that of the "normal" orientation, [Formula: see text] by 800 ± 300 cal mol−1.

scholarly journals Crystallographic features of ammonium fluoroelpasolites: dynamic orientational disorder in crystals of (NH4)3HfF7 and (NH4)3Ti(O2)F5

2017 ◽  
Vol 73 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Anatoly A. Udovenko ◽  
Alexander A. Karabtsov ◽  
Natalia M. Laptash
Keyword(s):  
Single Crystal ◽  
Electron Density ◽  
Diffraction Data ◽  
Central Atom ◽  
X Ray Diffraction ◽  
Dynamic Nature ◽  
Orientational Disorder ◽  
High Quality ◽  
Structural Units ◽  
X Ray

A classical elpasolite-type structure is considered with respect to dynamically disordered ammonium fluoro-(oxofluoro-)metallates. Single-crystal X-ray diffraction data from high quality (NH4)3HfF7 and (NH4)3Ti(O2)F5 samples enabled the refinement of the ligand and cationic positions in the cubic Fm \bar 3 m (Z = 4) structure. Electron-density atomic profiles show that the ligand atoms are distributed in a mixed (split) position instead of 24e. One of the ammonium groups is disordered near 8c so that its central atom (N1) forms a tetrahedron with vertexes in 32f. However, a center of another group (N2) remains in the 4b site, whereas its H atoms (H2) occupy the 96k positions instead of 24e and, together with the H3 atom in the 32f position, they form eight spatial orientations of the ammonium group. It is a common feature of all ammonium fluoroelpasolites with orientational disorder of structural units of a dynamic nature.

Thermal behaviour of alum-(K) KAl(SO4)2·12H2O from in situ laboratory high-temperature powder X-ray diffraction data: thermal expansion and modelling of the sulfate orientational disorder

2015 ◽  
Vol 79 (1) ◽  
pp. 157-170 ◽  
Author(s):  
Paolo Ballirano
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Diffraction Data ◽  
Bond Valence ◽  
X Ray Diffraction ◽  
Orientational Disorder ◽  
X Ray ◽  
Disorder Parameter ◽  
Bond Valence Sum

AbstractThe present work analyses the thermal behaviour of alum-(K), KAl(SO4)2·12H2O, by in situ laboratory high-temperature powder X-ray diffraction data from 303 K to melting, which starts at 355 K and is completed, due to kinetics, at 359 K. The calculated a0 linear thermal expansion coefficient is of 14.68(11) × 10–6 K–1 within the investigated thermal range. The k disorder parameter, describing the extension of the orientational disorder of the sulfate group, has been found to decrease from ∼0.70 to ∼0.65 just before melting. It has been demonstrated that the occurrence of the disorder implies the coexistence of K+ ions in both six- and seven-fold coordination. This is necessary for assigning a reasonable bond-valence sum of 0.81 valence units (vu) to the 'average' K+ ion a instead of 0.66 vu, which is obtained in the case of six-fold coordination alone. We can describe the temperature dependence of k from 93–355 K by means of the empirical equation k = 0.798(12) + 2.5(11) × 10–4 T – 1.9(2) × 10–6T2, which includes reference low-temperature data. Bond-valence analysis has shown that, on cooling, an increase of the k disorder parameter and shortening of the K–O2 bond distance act together to maintain constancy in the bond-valence sum at the K site, stabilizing the structure. Therefore, the need for keeping the 'average' K+ ion at a reasonable bond-valence sum appears to be the driving force for the ordering process involving the sulfate group.

X-ray characterization of Mg, Fe, and Mn natural end-members of the axinite group

2000 ◽  
Vol 15 (3) ◽  
pp. 180-188 ◽  
Author(s):  
Gabriella Salviulo ◽  
Giovanni B. Andreozzi ◽  
Giorgio Graziani
Keyword(s):  
Diffraction Data ◽  
Crystal Chemical ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Normal Orientation ◽  
Fe And Mn ◽  
Chemical Studies ◽  
End Members

New powder X-ray diffraction data for magnesio-, ferro-, and manganaxinite, obtained from samples closely corresponding to the three end-members of the axinite mineral group, were obtained using a conventional Bragg–Brentano diffractometer. Space group is P 1¯. Powder patterns were indexed using Peacock's normal orientation, which gave: a=7.1381(3), b=9.1626(4), c=8.9421(4) Å, α=91.903(4), β=98.105(3), γ=77.468(4)° for magnesioaxinite; a=7.1479(4), b=9.1962(5), c=8.9576(4) Å, α=91.857(4), β=98.177(4), γ=77.359(4)° for ferroaxinite, and a=7.1849(4), b=9.2152(5), c=8.9765(4) Å, α=91.761(4), β=98.153(4), γ=77.150(4)° for manganaxinite. Peacock's orientation has been adopted in all recent structural and crystal chemical studies of axinite, but it differs from that reported on the JCPDS cards (29-344, 27-076 and 27-084, respectively). New data include an increased number of indexed peaks.

scholarly journals High-pressure synthesis and crystal structure of the mixed-cation borate Ga4In4B15O33(OH)3

2019 ◽  
Vol 74 (4) ◽  
pp. 357-363
Author(s):  
Daniela Vitzthum ◽  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Mixed Cation ◽  
High Pressure High Temperature ◽  
Pressure Synthesis

AbstractThe mixed cation triel borate Ga4In4B15O33(OH)3 was synthesized in a Walker-type multianvil apparatus at high-pressure/high-temperature conditions of 12.5 GPa and 1300°C. Although the product could not be reproduced in further experiments, its crystal structure could be reliably determined via single-crystal X-ray diffraction data. Ga4In4B15O33(OH)3 crystallizes in the tetragonal space group I41/a (origin choice 2) with the lattice parameters a = 11.382(2), c = 15.244(2) Å, and V = 1974.9(4) Å3. The structure of the quaternary triel borate consists of a complex network of BO4 tetrahedra, edge-sharing InO6 octahedra in dinuclear units, and very dense edge-sharing GaO6 octahedra in tetranuclear units.

Crystallization and preliminary x-ray diffraction data of the cryptomonad biliprotein phycocyanin-645 from a Chroomonas spec.

1984 ◽  
Vol 140 (2-3) ◽  
pp. 202-205 ◽  
Author(s):  
Walter Morisset ◽  
Werner Wehrmeyer ◽  
Tilman Schirmer ◽  
Wolfram Bode
Keyword(s):  
Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray

Theoretically derived thermodynamic properties can be improved by the refinement of low-frequency modes against X-ray diffraction data

2021 ◽  
Author(s):  
Anna Agnieszka Hoser ◽  
Marcin Sztylko ◽  
Damian Trzybiński ◽  
Anders Østergaard Madsen
Keyword(s):  
Thermodynamic Properties ◽  
Dft Calculations ◽  
Diffraction Data ◽  
Molecular Crystals ◽  
Low Frequency ◽  
X Ray Diffraction ◽  
X Ray ◽  
Efficient Approach

A framework for estimation of thermodynamic properties for molecular crystals via refinement of frequencies from DFT calculations against X-ray diffraction data is presented. The framework provides an efficient approach to...

Single-crystal investigation of Ce5AgxGe4−x (x = 0.1−1.08) with Sm5Ge4 type

2020 ◽  
Vol 75 (8) ◽  
pp. 765-768
Author(s):  
Bohdana Belan ◽  
Dorota Kowalska ◽  
Mariya Dzevenko ◽  
Mykola Manyako ◽  
Roman Gladyshevskii
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Diffraction Data ◽  
Binary Compound ◽  
Lattice Parameters ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray

AbstractThe crystal structure of the phase Ce5AgxGe4−x (x = 0.1−1.08) has been determined using single-crystal X-ray diffraction data for Ce5Ag0.1Ge3.9. This phase is isotypic with Sm5Ge4: space group Pnma (No. 62), Pearson code oP36, Z = 4, a = 7.9632(2), b = 15.2693(5), c = 8.0803(2) Å; R1 = 0.0261, wR2 = 0.0460, 1428 F2 values and 48 variables. The two crystallographic positions 8d and 4c show Ge/Ag mixing, leading to a slight increase in the lattice parameters as compared to those of the pure binary compound Ce5Ge4.

The modulated structure of Bi2Sr3−xCaxCu2O8: A commensurate model from single crystal X-ray diffraction data

1989 ◽  
Vol 161 (5-6) ◽  
pp. 598-606 ◽  
Author(s):  
G. Calestani ◽  
C. Rizzoli ◽  
M.G. Francesconi ◽  
G.D. Andreetti
Keyword(s):  
Single Crystal ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Modulated Structure ◽  
X Ray
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