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On the temperature dependence of H‐ U iso in the riding hydrogen model
Author(s) -
Lübben Jens,
Volkmann Christian,
Grabowsky Simon,
Edwards Alison,
Morgenroth Wolfgang,
Fabbiani Francesca P. A.,
Sheldrick George M.,
Dittrich Birger
Publication year - 2014
Publication title -
acta crystallographica section a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.742
H-Index - 83
ISSN - 2053-2733
DOI - 10.1107/s2053273314010626
Subject(s) - neutron diffraction , atom (system on chip) , hydrogen atom , crystallography , diffraction , synchrotron , hydrogen , materials science , chemistry , thermodynamics , physics , crystal structure , group (periodic table) , nuclear physics , optics , organic chemistry , computer science , embedded system
The temperature dependence of H‐ U iso in N ‐acetyl‐L‐4‐hydroxyproline monohydrate is investigated. Imposing a constant temperature‐independent multiplier of 1.2 or 1.5 for the riding hydrogen model is found to be inaccurate, and severely underestimates H‐ U iso below 100 K. Neutron diffraction data at temperatures of 9, 150, 200 and 250 K provide benchmark results for this study. X‐ray diffraction data to high resolution, collected at temperatures of 9, 30, 50, 75, 100, 150, 200 and 250 K (synchrotron and home source), reproduce neutron results only when evaluated by aspherical‐atom refinement models, since these take into account bonding and lone‐pair electron density; both invariom and Hirshfeld‐atom refinement models enable a more precise determination of the magnitude of H‐atom displacements than independent‐atom model refinements. Experimental efforts are complemented by computing displacement parameters following the TLS+ONIOM approach. A satisfactory agreement between all approaches is found.