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In fact none of the SHELX programs care whether the data have been
merged, they will merge automatically if necessary, but there is an
advantage in using unmerged data for SHELXC because it enables better
diagnostic statistics. Similarly it doesn't matter for any SHELX program
what order the data are in and whether systematic absences have been
removed (though I prefer to keep them in because they help XPREP to
deduce the space group automatically and anyway you may later decide to
change the space group).
One tactical advantage of inputting merged data for SHELXL refinement is
that it simplifies the handling of the free R flags. The SHELX option in
mtz2various can be used to keep the same flags, but unfortunately the
file this produces needs some hand editing before SHELXL can read it. If
you use XPREP to determine the space group (if necessary with an axis
transformation) and then merge the data, it will prompt you for how to
set the free R flags when writing the .hkl file for input to SHELXL;
alternatively XPREP can be used to tranfer free R flags from one file to
another.
George
Eleanor Dodson wrote:
Do you mean "unmerged"
or
a file containing
h k l I(+)
-h -k -l I(-)
You can generate the second from MTZ"VARIOUS by assigning I+ and I-
Eleanor
Nat Echols wrote:
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A coworker recently solved a structure at high resolution with
multiple anomalous scatterers bound. He'll be using SHELXL eventually,
and we'd like to try incorporating the anomalous differences
(especially since he'll be refining against intensities). I understand
how to do this from the perspective of SHELXL, but I don't know how to
make a reflections file from what we have now. The MTZ file (from
HKL2000->scalepack2mtz) has the columns I(+) SIGI(+) I(-) SIGI(-); how
do I go from this to an "unmerged" set of reflections using
mtz2various? Space group is P212121, if that matters.
thanks,
Nat
--
Prof. George M. Sheldrick FRS
Dept. Structural Chemistry,
University of Goettingen,
Tammannstr. 4,
D37077 Goettingen, Germany
Tel. +49-551-39-3021 or -3068
Fax. +49-551-39-2582
