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Re: [sdpd] Recent Congress and comiing ones about SDPD
Jon Wright wrote:
> How about using texture or thermal expansion for the indexing problem as
> well? For the former case systematic variations in intensity relate
> lines to each other and give some indication about directions in
> reciprocal space. For the latter case systematic shifts in peak
> positions relate lines together and generate similar information.
> D'Yvoire indexed FeAsO4 by doing cation/anion substitutions and
> generating systematic lineshifts more than 30 years ago (C. R. Acad. Sc.
> Paris, 1972 275C 949) and temperature can do the same thing where the
> chemistry is more resticted.
Vand, Aitken and Campbell used powder measurements at two different temperatures
to facilitate indexing in their publication from 1949 (Acta Cryst. 2, p.
398-403).
They used the chemistry of their compound(s) for indexing too: they worked on
the homologously isomorphous series Ag+ CH3-[CH2]m-COO-, in which only the
c-axis changes as a function of m (for m = 6, 8, 10, 12, 14, 16, 18). (In
addition, these compounds exhibit more than average texture due to the
plate-like morphology of the crystals, but that information was not used.)
They also used the fact that the compounds are homologously isomorphous to note
the resemblance between their compounds and n-alkanes and suggest a crystal
structure.
Best wishes,
--
Jacco van de Streek
Research Scientist
Cambridge Crystallographic Data Centre
Cambridge, United Kingdom
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