Publication Date:
2021-03-29
Description:
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.
Keywords:
riding hydrogen model; QM/MM computations; neutron diffraction; invariom refinement; Hirshfeld-atom refinement; synchrotron radiation
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551
Language:
English
Type:
article
,
publishedVersion
