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Re: [sdpd] Hydrogen atoms and SDPD from X-ray data
Some remarks on H atoms in SDPD for organic compounds:
1) The H bond pattern should be visible, even if the H atoms are only on
calculated positions. If the resulting H bond pattern is not chemically
sensible, probably the H atoms are somewhere else.
2) A lattice-energy minimisation using dispersion-corrected DFT
calculations would prove (or disprove!) the structure.
3) We prefer to include the H atoms in the refinement using restraints. If
necessary, at the end, the positions of the H atoms could be optimized
(e.g. by force-field calculations fixing all non-H-atoms), followed by a
final Rietveld refinement with fixed H atom positions.
4) Lab data may be sufficient even to determine the tautomeric form, see
e.g.
S.L. Bekö et al, "X-ray powder diffraction, solid-state NMR and
dispersion-corrected DFT calculations to investigate the solid-state
structure of 2-ammonio-5-chloro-4-methylbenzenesulfonate", Z. Krist. 2010,
225, 382-387.
Best regards,
Martin Schmidt
--
Prof. Dr. Martin U. Schmidt
Institut für Anorganische und Analytische Chemie
der Universität Frankfurt
Max-von-Laue-Str. 7
D-60438 Frankfurt
Tel.: (069) 798 29171
Fax: (069) 798 29235
e-mail: m.schmidt...@chemie.uni-frankfurt.de
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