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Low‐temperature powder X‐ray diffraction measurements in vacuum: analysis of the thermal displacement of copper
Author(s) -
Wahlberg Nanna,
Bindzus Niels,
Christensen Sebastian,
Becker Jacob,
Dippel Ann-Christin,
Jørgensen Mads Ry Vogel,
Iversen Bo Brummerstedt
Publication year - 2016
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s1600576715022621
Subject(s) - copper , powder diffractometer , diffraction , displacement (psychology) , diffractometer , powder diffraction , liquid nitrogen , materials science , analytical chemistry (journal) , anharmonicity , helium , thermal , chemistry , thermodynamics , atomic physics , crystallography , condensed matter physics , physics , optics , metallurgy , crystal structure , psychology , organic chemistry , psychotherapist , chromatography
A serious limitation of the all‐in‐vacuum diffractometer reported by Straasø, Dippel, Becker & Als‐Nielsen [ J. Synchrotron Rad. (2014), 21 , 119–126] has so far been the inability to cool samples to near‐cryogenic temperatures during measurement. The problem is solved by placing the sample in a jet of helium gas cooled by liquid nitrogen. The resulting temperature change is quantified by determining the change in unit‐cell parameter and atomic displacement parameter of copper. The cooling proved successful, with a resulting temperature of ∼95 (3) K. The measured powder X‐ray diffraction data are of superb quality and high resolution [up to sinθ/λ = 2.2 Å −1 ], permitting an extensive modelling of the thermal displacement. The anharmonic displacement of copper was modelled by a Gram–Charlier expansion of the temperature factor. As expected, the corresponding probability distribution function shows an increased probability away from neighbouring atoms and a decreased probability towards them.