On the temperature dependence of H‐Uiso in the riding hydrogen model. Issue 4 (27th May 2014)

• Record Type: Journal Article
• Authors: Lübben, Jens; Volkmann, Christian; Grabowsky, Simon; Edwards, Alison; Morgenroth, Wolfgang; Fabbiani, Francesca P. A.; Sheldrick, George M.; Dittrich, Birger
• Is Part Of: Acta crystallographica. Volume 70:Issue 4(2014:Jul.)
• Page Start: 309
• Page End: 316
• Publication Date: 2014-05-27
• Subjects: Crystallography -- Periodicals; Condensed matter -- Periodicals; 548
• DOI: 10.1107/S2053273314010626
• Languages: English
• ISSNs: 2053-2733

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The temperature dependence of H‐<italic>U</italic>_iso in <italic>N</italic>‐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‐<italic>U</italic>_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.</p> </abstract>