On the temperature dependence of H-U iso in the riding hydrogen model
Lübben, Jens
Volkmann, Christian
Grabowsky, Simon
Edwards, Alison
Morgenroth, Wolfgang
Fabbiani, Francesca P. A.
Sheldrick, George M.
Dittrich, Birger
70, 4: 309 - 316
DOI: https://doi.org/10.1107/S2053273314010626
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/6723
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/6723
Lübben, Jens; Volkmann, Christian; Grabowsky, Simon; Edwards, Alison; Morgenroth, Wolfgang; Fabbiani, Francesca P. A.; Sheldrick, George M.; Dittrich, Birger, 2014: On the temperature dependence of H-U iso in the riding hydrogen model. In: Acta Crystallographica Section A Foundations and Advances, Band 70, 4: 309 - 316, DOI: 10.1107/S2053273314010626.
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The temperature dependence of H-Uiso 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-Uiso 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.
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