Dear Pavel,
May I suggest that you take a look at the SHELX manual:
http://shelx.uni-ac.gwdg.de/SHELX/shelx.pdf
before sending your SHELX questions to CCP4bb? You might
even find some good ideas for implementing in phenix_refine!
For example,
if you look up 'non-crystallographic symmetry' in the index
you will discover that SHELXL applies NCS in the form of
restraints, not constraints, which has the advantage that it
can be applied locally and in combination with all other
restraints and constraints involving the same atoms. However
you will not find TLS in the index, because the credit for
implementing this very useful concept should be given to
Martin Winn, Garib and Ethan, long after the current version
of SHELXL (and its manual) were released in 1997. And because
SHELXL only reads one instruction file (*.ins) and one
reflection file (*.hkl) but no other data files or libraries,
and FORTRAN will always be FORTRAN, the deposition of these
two files would be sufficient to define the refinement for
posterity.
Best wishes, George
Prof. George M. Sheldrick FRS
Dept. Structural Chemistry,
University of Goettingen,
Tammannstr. 4,
D37077 Goettingen, Germany
Tel. +49-551-39-3021 or -3068
Fax. +49-551-39-22582
On Wed, 15 Sep 2010, Pavel Afonine wrote:
> Dear Felix,
>
> > Shortly Shelxl knows crystallography best.
>
> I have no doubts about this. May questions were, though:
>
> > > - how .ins file encodes the information about NCS groups used in
> > > refinement (atom selection for NCS groups, restraint weights for different
> > > groups, etc?
> > >
> > > - how .ins file encodes the information about TLS (again, atom selections
> > > for TLS groups, TLS matrices, etc)? Related, does it have a concept of
> > > having TLS and other components to the total atomic displacement parameter
> > > (ADP)?
> > >
> > > - If I recall it correctly, to fix (=not refine) a certain parameter (say
> > > occupancy or B-factor) in Shelxl you need to add a number 10 to it. Is it
> > > true? IMHO, this might lead to confusion if such a file gets deposited to
> > > PDB.
>
> Best,
> Pavel.
>
>
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