scholarly journals Use of Extinction Corrections in Neutron Diffraction Experiments

1988 ◽  
Vol 41 (3) ◽  
pp. 383 ◽  
Author(s):  
A Delapalme
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Experimental Evidence ◽  
Diffraction Data ◽  
Structure Factor ◽  
Lorentz Factor ◽  
Relative Importance ◽  
Diffraction Experiment ◽  
Neutron Diffraction Data ◽  
Neutron Diffraction Experiment

The study of extinction by neutrons reveals many features of the extinction problem: theory and practical cases, polarised and unpolarised neutron cases. Special attention is given to the usual extinction corrections for neutron diffraction experiments, showing the relative importance of structure factor, wavelength, Lorentz factor, mosaic and the path of neutrons through the crystal. Two problems are reviewed: (a) how to detect the presence of extinction in both cases of a single crystal experiment with polarised and unpolarised neutrons; and (b) after experimental evidence for extinction in a neutron diffraction experiment, how to follow a reliable way to correct the neutron diffraction data in both cases of polarised and unpolarised neutron experiments. Some examples are given.

Single-crystal neutron diffraction of urea-phosphoric acid: evidence for H-atom migration in a short hydrogen bond between 150 K and 350 K

2001 ◽  
Vol 216 (6) ◽  
Author(s):  
C. C. Wilson ◽  
K. Shankland ◽  
N. Shankland
Keyword(s):  
Hydrogen Bond ◽  
Neutron Diffraction ◽  
Phosphoric Acid ◽  
Single Crystal ◽  
Diffraction Data ◽  
Neutron Diffraction Data ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Short Hydrogen Bond ◽  
Atom Migration

AbstractThe structure of urea-phosphoric acid has been refined using single-crystal neutron diffraction data collected at seven temperatures in the range 150 K to 350 K. The structure is orthorhombic, space group

Structure of Ce2Pt6Ga15: interplanar disorder from the Ce2Ga3 layers

1996 ◽  
Vol 52 (4) ◽  
pp. 580-585 ◽  
Author(s):  
G. H. Kwei ◽  
A. C. Lawson ◽  
A. C. Larson ◽  
B. Morosin ◽  
E. M. Larson ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Diffuse Scattering ◽  
Heavy Fermion ◽  
Neutron Diffraction Data ◽  
Crystal Data ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
A Cell

The structure of the heavy fermion compound Ce2Pt6Ga15 has been determined from neutron powder and X-ray/neutron single-crystal diffraction. Examination of symmetry equivalence among the single-crystal data, as well as the good fit of the powder data to the final structural arrangement, with all the atoms on symmetry sites, suggests that the correct space group is P63/mmc. The structure is unusual in that Ce layers have 1/3 of the Ce atoms replaced by groups of three Ga atoms; distances between atoms in these planes suggest this substitution must occur in a concerted fashion. The refined occupancies lead to a stoichiometry near Ce2Pt6Ga15, consistent with such an arrangement. In addition, single-crystal neutron diffraction data show columns of weak diffuse scattering along the <001> axes, suggesting disorder arising from a lack of registration of successive Ce2Ga3 layers (lying half a cell length or 8.27 Å apart along z) and a 3 × 3 × 1 supercell. This disorder is very likely responsible for the low resistance ratio of approximately unity measured for single-crystal samples.

Neutron diffraction experiment with the Y116S variant of transthyretin using iBIX at J-PARC: application of a new integration method

2020 ◽  
Vol 76 (11) ◽  
pp. 1050-1056
Author(s):  
Katsuhiro Kusaka ◽  
Takeshi Yokoyama ◽  
Taro Yamada ◽  
Naomine Yano ◽  
Ichiro Tanaka ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Data ◽  
Amyloid Fibrils ◽  
Integration Method ◽  
Proton Accelerator ◽  
Diffraction Experiment ◽  
Wild Type ◽  
Neutron Diffraction Experiment ◽  
X Ray ◽  
Attr Amyloidosis

Transthyretin (TTR) is one of more than 30 amyloidogenic proteins, and the amyloid fibrils found in patients afflicted with ATTR amyloidosis are composed of this protein. Wild-type TTR amyloids accumulate in the heart in senile systemic amyloidosis (SSA). ATTR amyloidosis occurs at a much younger age than SSA, and the affected individuals carry a TTR mutant. The naturally occurring amyloidogenic Y116S TTR variant forms more amyloid fibrils than wild-type TTR. Thus, the Y116S mutation reduces the stability of the TTR structure. A neutron diffraction experiment on Y116S TTR was performed to elucidate the mechanism of the changes in structural stability between Y116S variant and wild-type TTR through structural comparison. Large crystals of the Y116S variant were grown under optimal crystallization conditions, and a single 2.4 mm3 crystal was ultimately obtained. This crystal was subjected to time-of-flight (TOF) neutron diffraction using the IBARAKI biological crystal diffractometer (iBIX) at the Japan Proton Accelerator Research Complex, Tokai, Japan (J-PARC). A full data set for neutron structure analysis was obtained in 14 days at an operational accelerator power of 500 kW. A new integration method was developed and showed improved data statistics; the new method was applied to the reduction of the TOF diffraction data from the Y116S variant. Data reduction was completed and the integrated intensities of the Bragg reflections were obtained at 1.9 Å resolution for structure refinement. Moreover, X-ray diffraction data at 1.4 Å resolution were obtained for joint neutron–X-ray refinement.

Short Range Triplet Correlations in Krypton Near the Critical Point

1973 ◽  
Vol 51 (18) ◽  
pp. 1965-1970 ◽  
Author(s):  
D. J. Winfield ◽  
P. A. Egelstaff
Keyword(s):  
Correlation Function ◽  
Neutron Diffraction ◽  
Diffraction Data ◽  
Structure Factor ◽  
Short Range ◽  
Neutron Diffraction Data ◽  
Pressure Derivative ◽  
First Approximation ◽  
Triplet Correlation ◽  
Triplet Correlation Function

Neutron diffraction data have been taken for two states on the 218 °K isotherm of krypton. The isothermal pressure derivative of the fluid structure factor is interpreted in terms of the triplet correlation function using an expansion due to Abe. It is concluded that three terms in Abe's expansion explain the data to a first approximation, but significant discrepancies remain.

scholarly journals Low-temperature crystal structure of the unconventional spin-triplet superconductor UTe2 from single-crystal neutron diffraction

2020 ◽  
Vol 76 (1) ◽  
pp. 137-143 ◽  
Author(s):  
Vladimir Hutanu ◽  
Hao Deng ◽  
Sheng Ran ◽  
Wesley T. Fuhrman ◽  
Henrik Thoma ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Linear Thermal Expansion ◽  
The Body ◽  
Superconducting Transition ◽  
Neutron Diffraction Data ◽  
Spin Triplet

The crystal structure of a new superconductor UTe2 has been investigated using single-crystal neutron diffraction for the first time at the low temperature (LT) of 2.7 K, just above the superconducting transition temperature of ∼1.6 K, in order to clarify whether the orthorhombic structure of type Immm (No. 71), reported for the room-temperature (RT) structure persists down to the superconducting phase and can be considered as a parent symmetry for the development of spin-triplet superconductivity. In contrast to the previously reported phase transition at about 100 K [Stöwe (1996). J. Solid State Chem. 127, 202–210], our high-precision LT neutron diffraction data show that the body-centred RT symmetry is indeed maintained down to 2.7 K. No sign of a structural change from RT down to 2.7 K was observed. The most significant change depending on temperature was observed for the U ion position and the U–U distance along the c direction, implying its potential importance as a magnetic interaction path. No magnetic order could be deduced from the neutron diffraction data refinement at 2.7 K, consistent with bulk magnetometry. Assuming normal thermal evolution of the lattice parameters, moderately large linear thermal expansion coefficients of about α = 2.8 (7) × 10−5 K−1 are estimated.

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