TY  - JOUR
A1  - Lübben, Jens
A1  - Volkmann, Christian
A1  - Grabowsky, Simon
A1  - Edwards, Alison
A1  - Morgenroth, Wolfgang
A1  - Fabbiani, Francesca P. A.
A1  - Sheldrick, George M.
A1  - Dittrich, Birger
T1  - On the temperature dependence of H-U iso in the riding hydrogen model
Y1  - 2014
VL  - 70
IS  - 4
SP  - 309
EP  - 316
JF  - Acta Crystallographica Section A Foundations and Advances
DO  - 10.1107/S2053273314010626
DO  - 10.23689/fidgeo-2410
N2  - 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.
UR  - http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/6723
ER  -