[sdpd] Re: [PowBase]

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

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.

CIF Homepage at:
   http://www.se.iucr.org/iucr-top/cif/
Powder CIF Dictionary 
   http://www.se.iucr.org/iucr-top/cif/pd/
 Example Powder CIF Submission (no raw data)
   ftp://ftp.iucr.org/pub/rietxmpl.cif

When/if powder programs are CIF friendly, the viewer used
could be up to the user - i.e., viewing in Q space in 
programs such as Winplotr.
   http://www-llb.cea.fr/winplotr/winplotr.htm
   http://www.ccp14.ac.uk/ccp/web-mirrors/plotr/winplotr/winplotr.htm

----

(I should also declare a possible conflict of interest here as
according to an Email from Brian Toby of June 1998, I am on
the Powder CIF Dictionary Management Group)

While CIF can be painful to initially program for(?),
based on experiences with small molecule single crystal
data transfer, it could solve a lot of problems with
data transfer if properly used in the powder community.

----

Initially, it would be nice if authors of the common
powder data conversion software packages such as 
ConvX, Powder v2.0, Winfit, PowderX, etc could be
persuaded to be able to include the ability to import
and export CIF.  Though to be practical, CIF friendliness
should be pushed for any current and up to date Powder 
Program.

Lachlan.

PS: I should note that the shareware Cryscon for Windows software 
by Eric Dowty can import and export CIF structure files. 
(as well as CCDC, Shelx, DBWS, LHPM, ICSD, ORTEP, 
RIETAN, GSAS and Fullprof)
   http://www.shapesoftware.com/#anchor_cryscon
   http://www.ccp14.ac.uk/ccp/web-mirrors/shape/#anchor_cryscon

> Perhaps we should also return to one of the old chestnuts (quaint English
> expression that means 'classic argument') from the powder diffraction meeting
> a while back- should we standardise the data by presenting it in d or q
> (irrespective of whether the fit was done in 2theta or TOF, etc)?- This can
> only simplify comparisions of data.
> 
> 
> Can I make a few suggestions:
> 
> 1) Give the wavelength(s) in Angstroms, with ratios,  so that lab source and
> neutron people can understand each other (Cu k-alpha and PG(002) both require
> 'specialised' knowledge).
> 
> 2) Allow the reader to browse through the formula.
> 
> 3) If people are to quickly check out the data we either need to have some
> standardised viewers (or data format), or a ps/pdf/jpeg picture of the
> pattern. Again d spacing or q might be useful to aid comparisons between
> wavelengths.
> 

-- 
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