International
Tables for
Crystallography
Volume H
Powder diffraction
Edited by C. J. Gilmore, J. A. Kaduk and H. Schenk

International Tables for Crystallography (2018). Vol. H, ch. 2.7, p. 164

Section 2.7.10. Sample preparation

A. Katrusiaka*

aFaculty of Chemistry, Adam Mickiewicz University, Poznań, Poland
Correspondence e-mail: katran@amu.edu.pl

2.7.10. Sample preparation

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Several basic techniques can be used to prepare a sample for a high-pressure experiment, for example:

  • (i) A solid sample can be mounted under ambient conditions in the high-pressure chamber together with the hydrostatic fluid, then sealed and pressurized;

  • (ii) A solid sample can be mounted under ambient conditions in the high-pressure chamber, condensed gas loaded at elevated pressure (Tkacz, 1995[link]; Rivers et al., 2008[link]; Couzinet et al., 2003[link]; Mills et al., 1980[link]; Yagi et al., 1996[link]; Kenichi et al., 2001[link]) or under cryogenic conditions, and the sample sealed and further pressurized by gasket compression;

  • (iii) A liquid sample can fill the whole chamber volume under ambient conditions, or condensed gases or their mixtures can be loaded at elevated pressure, and after sealing the DAC the sample is frozen under isothermal conditions;

  • (iv) A crystal of the pure compound or of a solvate can precipitate from the mixture (solution) when compressed isothermally – the crystal can be in the form of a single crystal or a powder, fully or partly filling the DAC chamber;

  • (v) Samples completely filling the DAC chamber can be compressed isothermally or undergo isochoric treatment, but strains can be generated in a single crystal or in the grains of a compressed powder conglomerate by anisotropic thermal contraction/expansion; this strain can be avoided by having an excess of the hydrostatic component of the mixture;

  • (vi) A solid powdered sample can be mixed with a powder of another compound, which is much softer than the sample and is used as a pseudo-hydrostatic medium (halite and MgO are often used for this purpose) – this technique is mainly used for cubic or isotropic samples in large-volume presses, where (pseudo)isotropic strain and pseudo-spherical compression minimize the effect of preferential orientation in the sample.

Preferential orientation can significantly hamper the quality of powder diffraction data, and corrections for this effect should be applied in the Rietveld refinement. All Rietveld refinement programs include preferential orientation models, which fit the data with satisfactory results (McMahon, 2004[link], 2005[link]; Filinchuk, 2010[link]).

References

Couzinet, B., Dahan, N., Hamel, G. & Chervin, J.-C. (2003). Optically monitored high-pressure gas loading apparatus for diamond anvil cells. High Press. Res. 23, 409–415.Google Scholar
Filinchuk, Y. (2010). Light metal hydrates under non-ambient conditions: probing chemistry by diffraction? In High-Pressure Crystallography. From Fundamental Phenomena to Technological Applications, edited by E. Boldyreva & P. Dera, pp. 281–291. Dordrecht: Springer.Google Scholar
Kenichi, T., Sahu, P. Ch., Yoshiyasu, K. & Yasuo, T. (2001). Versatile gas-loading system for diamond-anvil cells. Rev. Sci. Instrum. 72, 3873–3876.Google Scholar
McMahon, M. I. (2004). High pressure diffraction from good powders, poor powders and poor single crystals. In High-Pressure Crystallography, edited by A. Katrusiak & P. F. McMillan, pp. 1–20. Dordrecht: Kluwer. Google Scholar
McMahon, M. I. (2005). Structures from powders and poor-quality single crystals at high pressure. J. Synchrotron Rad. 12, 549–553.Google Scholar
Mills, R. L., Liebenberg, D. H., Bronson, J. C. & Schmidt, L. C. (1980). Procedure for loading diamond cells with high-pressure gas. Rev. Sci. Instrum. 51, 891–895.Google Scholar
Rivers, M., Prakapenka, V. B., Kubo, A., Pullins, C., Holl, Ch. M. & Jacobsen, S. D. (2008). The COMPRES/GSECARS gas-loading system for diamond anvil cells at the Advanced Photon Source. High Press. Res. 28, 273–292.Google Scholar
Tkacz, M. (1995). Novel high-pressure technique for loading diamond anvil cell with hydrogen. Pol. J. Chem. 69, 1205.Google Scholar
Yagi, T., Yusa, H. & Yamakata, M. (1996). An apparatus to load gaseous materials to the diamond-anvil cell. Rev. Sci. Instrum. 67, 2981–2984.Google Scholar








































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