[sdpd] SDPD vs. small single crystals

[MartinUlrich.Schmidt...@de.clariant.com]

I think, SDPD will be valuable in future, even if diffraction on small
single crystal becomes available.

The determination of crystal structures from small singles crystals depends
on the crystal quality.
For samples like e.g. organic materials having no heay atom, limited
crystal qualities, twinning, stacking faults etc. powder diffraction still
remains the only method for structure determination.
Some weeks ago, we indeed had this case.
We got a nice-looking tranparent "single crystal"  with a size of
300*200*200 (!) micrometer. But the crystal quality was very poor (layer
structure with stacking faults + twinning, 33 non-hydrogen atoms, no heavy
atom). Even with a rotating anode and a CCD we could not determine the
crystal structure. Thus we solved the structure from powder data by energy
minimization in a few days. Perhaps it might have been possible to solve
the structure from the single crystal data too, but it was easier and
faster to use the powder data.

I think, with the new and improved methods for solving crystal structures
from powder data, SDPD will in several cases be just EASIER AND FASTER than
to grow a suitable single crystal.

Martin U. Schmidt



- - - - - - - -
Martin U. Schmidt
Clariant GmbH
Pigment Technology Research
G834
D-65926 Frankfurt a.M.
Germany
Tel.: 0049-69-305-13426
Fax: 0049-69-331749
E-Mail: MartinUlrich.Schmidt...@Clariant.com