Dear Frank,
DIRAX is very good at finding the twin lattices in case of non-merohedral
twinning. In the reticular case you might want to use the LEPAGE-TWIN routine
in PLATON to find the correct subcell.
My collegue, Martin Lutz, suggests to change the measurement temperature in
order to change the cell parameters and thus the amount of overlap.
For integration of the data you may want to use our EVAL15 (J. Appl. Cryst. 43
(2010) 70-82).
Have a look at http://www.crystal.chem.uu.nl/distr/
EVAL15 can deconvolute reflections with significant overlap, or otherwise
outputs the summed intensties of the two reflections. This method is
particularly suitable for your reticular case. Scaling can be done with TWINABS
and refinement can be done with SHELX (hklf5 format).
Loes.
P.S. a collection of twinning literature can be found at
http://www.cryst.chem.uu.nl/lutz/twin/gen_twin.html
On 06/23/10 11:46, Frank von Delft wrote:
My experience with pseudo-merohedral twinning (it was actually the
reticular case with half the spots overlapped and the other
non-overlapped half on a pseudo C-centred lattice) is that the degree
of splitting varies widely over the diffraction pattern. In some
places there was complete overlap, in others you see elongation of the
spots, in others partial separation, and in others complete separation
(and of course all shades in-between), with around 50-50 intensity
split. In this situation the mosaicity becomes meaningless! I'm not
aware of any software that can handle this kind of thing successfully
(and certainly the data we did manage to get turned out to be
garbage!).
Both DIRAX or SAINT should be able to handle it, you'll need SADABS to
scale it. (The latter two are in the Bruker software.)
phx.
--
__________________________________________
Dr. Loes Kroon-Batenburg
Dept. of Crystal and Structural Chemistry
Bijvoet Center for Biomolecular Research
Utrecht University
Padualaan 8, 3584 CH Utrecht
The Netherlands
E-mail : l.m.j.kroon-batenb...@uu.nl
phone : +31-30-2532865
fax : +31-30-2533940
__________________________________________
