The effect of diffraction by the diamonds of a diamond-anvil cell on single-crystal sample intensities

1990 ◽  
Vol 23 (5) ◽  
pp. 392-396 ◽  
Author(s):  
J. S. Loveday ◽  
M. I. McMahon ◽  
R. J. Nelmes
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Diamond Anvil Cell ◽  
Structural Information ◽  
Wavelength Dependence ◽  
Single Crystal Sample ◽  
Data Sets ◽  
Crystal Sample ◽  
Diamond Anvil ◽  
Integrated Intensities

The integrated intensities measured in X-ray single-crystal high-pressure structural studies using a diamond-anvil cell are shown to be reduced substantially when the diamonds diffract at the same setting as the sample – by as much as 50% in some cases. The pressure and wavelength dependence of this process have been studied and also the effect of changing the beam divergence by the use of a synchrotron beam. The consequences for the accuracy of structural information derived from data sets collected at high pressure are considered and a data-collection strategy for detecting and avoiding the effects of diamond diffraction is proposed.

scholarly journals Use of a miniature diamond-anvil cell in a joint X-ray and neutron high-pressure study on copper sulfate pentahydrate

IUCrJ ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Giulia Novelli ◽  
Konstantin V. Kamenev ◽  
Helen E. Maynard-Casely ◽  
Simon Parsons ◽  
Garry J. McIntyre
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Diffraction Data ◽  
Diamond Anvil Cell ◽  
Structural Parameters ◽  
Structure Refinement ◽  
Neutron Data ◽  
X Ray ◽  
Sulfate Pentahydrate ◽  
Diamond Anvil

Single-crystal X-ray and neutron diffraction data are usually collected using separate samples. This is a disadvantage when the sample is studied at high pressure because it is very difficult to achieve exactly the same pressure in two separate experiments, especially if the neutron data are collected using Laue methods where precise absolute values of the unit-cell dimensions cannot be measured to check how close the pressures are. In this study, diffraction data have been collected under the same conditions on the same sample of copper(II) sulfate pentahydrate, using a conventional laboratory diffractometer and source for the X-ray measurements and the Koala single-crystal Laue diffractometer at the ANSTO facility for the neutron measurements. The sample, of dimensions 0.40 × 0.22 × 0.20 mm3 and held at a pressure of 0.71 GPa, was contained in a miniature Merrill–Bassett diamond-anvil cell. The highly penetrating diffracted neutron beams passing through the metal body of the miniature cell as well as through the diamonds yielded data suitable for structure refinement, and compensated for the low completeness of the X-ray measurements, which was only 24% on account of the triclinic symmetry of the sample and the shading of reciprocal space by the cell. The two data-sets were combined in a single `XN' structure refinement in which all atoms, including H atoms, were refined with anisotropic displacement parameters. The precision of the structural parameters was improved by a factor of up to 50% in the XN refinement compared with refinements using the X-ray or neutron data separately.

scholarly journals High Pressure Behavior of Mascagnite from Single Crystal Synchrotron X-ray Diffraction Data

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 976
Author(s):  
Paola Comodi ◽  
Maximiliano Fastelli ◽  
Giacomo Criniti ◽  
Konstantin Glazyrin ◽  
Azzurra Zucchini
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Room Temperature ◽  
Diamond Anvil Cell ◽  
Geometrical Parameters ◽  
X Ray Diffraction ◽  
Third Order ◽  
X Ray ◽  
Diamond Anvil ◽  
Murnaghan Equation

High-pressure synchrotron X-ray diffraction was carried out on a single crystal of mascagnite, compressed in a diamond anvil cell. The sample maintained its crystal structure up to ~18 GPa. The volume–pressure data were fitted by a third-order Birch–Murnaghan equation of state (BM3-EOS) yielding K0 = 20.4(7) GPa, K’0 = 6.1(2), and V0 = 499(1) Å3, as suggested by the F-f plot. The axial compressibilities, calculated with BM3-EOS, were K0a = 35(3), K’0a = 7.7(7), K0b = 10(3), K’0b = 7(1), K0c = 25(1), and K’0c = 4.3(2) The axial moduli measured using a BM2-EOS and fixing K’0 equal to 4, were K0a = 52(2), K0b = 20 (1), and K0c = 29.6(4) GPa, and the anisotropic ratio of K0a:K0b:K0c = 1:0.4:0.5. The evolution of crystal lattice and geometrical parameters indicated no phase transition until 17.6 GPa. Sulphate polyhedra were incompressible and the density increase of 30% compared to investigated pressure should be attributed to the reduction of weaker hydrogen bonds. In contrast, some of them, directed along [100], were very short at room temperature, below 2 Å, and showed a very low compressibility. This configuration explains the anisotropic compressional behavior and the lowest compressibility of the a axis.

scholarly journals Combined X-ray and neutron single-crystal diffraction in diamond anvil cells

2020 ◽  
Vol 53 (1) ◽  
pp. 9-14 ◽  
Author(s):  
Andrzej Grzechnik ◽  
Martin Meven ◽  
Carsten Paulmann ◽  
Karen Friese
Keyword(s):  
High Pressure ◽  
Data Processing ◽  
Single Crystal ◽  
Diamond Anvil Cell ◽  
Crystal Data ◽  
Structural Refinement ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Diamond Anvil ◽  
First Time

It is shown that it is possible to perform combined X-ray and neutron single-crystal studies in the same diamond anvil cell (DAC). A modified Merrill–Bassett DAC equipped with an inflatable membrane filled with He gas has been developed. It can be used on laboratory X-ray and synchrotron diffractometers as well as on neutron instruments. The data processing procedures and a joint structural refinement of the high-pressure synchrotron and neutron single-crystal data are presented and discussed for the first time.

scholarly journals Use of a miniature diamond-anvil cell in high-pressure single-crystal neutron Laue diffraction

IUCrJ ◽  
2016 ◽  
Vol 3 (3) ◽  
pp. 168-179 ◽  
Author(s):  
Jack Binns ◽  
Konstantin V. Kamenev ◽  
Garry J. McIntyre ◽  
Stephen A. Moggach ◽  
Simon Parsons
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Cell Body ◽  
Diamond Anvil Cell ◽  
Unexpected Finding ◽  
High Symmetry ◽  
X Rays ◽  
Laue Diffraction ◽  
X Ray ◽  
Diamond Anvil

The first high-pressure neutron diffraction study in a miniature diamond-anvil cell of a single crystal of size typical for X-ray diffraction is reported. This is made possible by modern Laue diffraction using a large solid-angle image-plate detector. An unexpected finding is that even reflections whose diffracted beams pass through the cell body are reliably observed, albeit with some attenuation. The cell body does limit the range of usable incident angles, but the crystallographic completeness for a high-symmetry unit cell is only slightly less than for a data collection without the cell. Data collections for two sizes of hexamine single crystals, with and without the pressure cell, and at 300 and 150 K, show that sample size and temperature are the most important factors that influence data quality. Despite the smaller crystal size and dominant parasitic scattering from the diamond-anvil cell, the data collected allow a full anisotropic refinement of hexamine with bond lengths and angles that agree with literature data within experimental error. This technique is shown to be suitable for low-symmetry crystals, and in these cases the transmission of diffracted beams through the cell body results in much higher completeness values than are possible with X-rays. The way is now open for joint X-ray and neutron studies on the same sample under identical conditions.

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