[sdpd] Re: RIET: Use of CIF as advocated by Lachlan

[L.M.D.Cranswick... @dl.ac.uk (L. Cranswick)]

(keeping the entire text of Robin's Email as it was not
Cc'd to the Rietveld list).

Robin Shirley (R.Shirley... @surrey.ac.uk) writes: 
> Lachlan Cranswick writes [Fri, 5 Nov 1999 17:59:40 +0000 (GMT)]:
> 
> > While the database system Armel has done looks good,,
> > this still leaves the problem of a common file
> > format.  If CIF was used, many of the problems/requests
> > described by Andrew would become non-issues.
> 
> I'm reluctant to take issue with Lachlan, who does such a good job at 
> the CCP14 website, and indeed publishes CRYSFIRE from there.
> 
> However, I have to say that I'd feel happier about supporting CIF as a common
> file format if (a) it were considerably simpler to read and (b) the CIF
> committee were more responsive to practical powder-related issues.
> 
> Firstly let me say that, in a spirit of general co-operation, several years
> ago I extended CRYS/CRYSFIRE to support a basic form of CIF as a file-save
> option (i.e. for output).
> 
> However I can't support it as an input format due to its excessive
> complexity.  I simply don't have the address space available in CRYS, and
> most of what's included in CIF would be irrelevant for this purpose.
> 
> Also, my attitude is partly coloured by the fact that, both at Beijing in 
> 1993 and at Seattle in 1996, I submitted a formal proposal concerning a small 
> set of Powder-CIF extensions which would cover issues connected with indexing
> (copies emailed on request), as at present these are not touched on.
> 
> On each occasion I took the precaution of first running them past Brian Toby 
> to confirm that their syntax was well formed.  And both times absolutely 
> nothing happened.  I didn't even receive the courtesy of an acknowledgement.
> 
> Brian told me at Seattle that the committee seemed to have lost the 1993
> proposals.  After resubmitting them, I again got no reply, so I didn't bother
> trying again at Edinburgh.
> 
> In the light of this, I'm afraid that as a software author I don't feel
> encouraged to put myself out to support CIF as a common file format, when
> the CIF committee rather gives the impression of living in an ivory tower 
> remote from actual users.
> 
> Robin Shirley
> School of Human Sciences
> University of Surrey
> UK
> 

For a sizable database, I don't see an alternative to CIF
for being able to transfer Crystallographic structure
and data information in a civilised manner (?)
(compared to having a dozen or so different formats where
things could become a mess quite quickly).   If not CIF,
then what?

(Does NEXUS just handle data - or can it include structure
information?)

-----

On the single crystal side, Louis Farrugia's CIF conversion
software is very solid; showing good CIF conversion can be done,
both in converting "structure" and "reflection" data into
WinGX's shelx format.
    http://www.chem.gla.ac.uk/~louis/software/
    http://www.ccp14.ac.uk/ccp/web-mirrors/farrugia/~louis/software/
    http://ccp14.sims.nrc.ca/ccp/web-mirrors/farrugia/~louis/software/

How much programming effort (hours, days?) would it considered
standard to be able to program in a CIF to X converter for
say GSAS or Fullprof, or X?  Is any source code available that
could be used as a template for powder authors?

Is there any instance of a powder program being able to
import a CIF into the program's native powder format?

Lachlan.

PS: With respect to Robin's comments on trying to get additions
to PowderCIF for Powder Indexing,;what is the present mechanism
for getting things implemented into the Powder CIF area?


-- 
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