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Re: Getting started

  • To: Multiple recipients of list <pddmg@iucr.org>
  • Subject: Re: Getting started
  • From: vondreele@lanl.gov (Bob Von Dreele)
  • Date: Tue, 23 Nov 1999 16:05:52 GMT
Dear Lachlan & others,
GSAS will write cif files but can't read them. The routine GSAS2CIF has
been worked over recently and does appear to successfully produce something
that at least superficially looks like a cif file. I'd appreciate any
comments one may have on the success or otherwise in using it and where it
can be improved. Somewhere on my TBD list is a CIF2GSAS routine but finding
time is the problem. One possible approach is to have facilities for
extracting just part of the information from the cif file while building a
GSAS exp file. I've already done this for PDB files, and there is a
GSAS2PDB routine. The most useful data in a cif file are the atoms and the
diffraction data. Hopefully, CIFtbx will be useful for this. Comments?
Bob
At 10:08 AM 11/23/99 +0000, you wrote:
>
>> Two comments. 
>> 
>> 1) There does exist a free FORTRAN subroutine library, CIFtbx
>> (http://www.iucr.org/iucr-top/cif/software/ciftbx/README.html). I do not
>> have much experience with it, but it looks pretty good to me. If CIFtbx
>> is flawed or insufficient, this does need to be addressed.
>> 
>> 2) I agree that a pdCIF file is not always that easy to read, since
>> there are many ways to record data and software will need to be
>> flexible. In the case of an indexing program, one will need to look for
>> peak positions as _pd_peak_2theta_maximum or _pd_peak_2theta_centroid or
>> _pd_peak_d_spacing. Of course it is OK to write a program that requires
>> that peak positions be specified as d-spaces. Obviously an indexing
>> program can't run if there is no peak table present. If one uses CIFtbx,
>> I don't think it requires much more than a few dozen lines of code to
>> pull in the peak positions and convert them, if needed. (BHT)
>
>One thing done by the  World Wide Web consortium (http://www.w3.org/)
>is to have a Web-browser they can hack at to show their latest
>suggestions/standards in action in a real software program.
>
>Under the assumption that there is at present not one Rietveld
>program that can both read/write good CIF for all occassions(?);
>is there any chance that a collaboration could be fixed with a 
>Rietveld author who might be interested in this - and thus
>find out what problems are encountered on the way to get a 
>full implementation?    A rietveld with open source code would
>be ideal but this may not be possible(?)
>
>Comments?
>
>Lachlan.
>
>-- 
>Lachlan M. D. Cranswick
>
>Collaborative Computational Project No 14 (CCP14)
>    for Single Crystal and Powder Diffraction
>Daresbury Laboratory, Warrington, WA4 4AD U.K
>Tel: +44-1925-603703  Fax: +44-1925-603124
>E-mail: l.cranswick@dl.ac.uk  Ext: 3703  Room C14
>                           http://www.ccp14.ac.uk

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