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CIF Powder Diffraction Dictionary Maintenance Group: Getting started

  • To: Multiple recipients of list <pddmg@iucr.org>
  • Subject: CIF Powder Diffraction Dictionary Maintenance Group: Getting started
  • From: "Brian H. Toby" <brian.toby@nist.gov>
  • Date: Fri, 19 Nov 1999 21:40:32 GMT
Dear pdDMG members,

   I apologize for the amount of time it has taken before getting
started with our group's task, to produce new versions of the powder
diffraction crystallographic information file (pdCIF) dictionary. This
is a funny task. CIF is an archive format, which means that while we can
refine the definition for a data item in the pdCIF dictionary, we cannot
significantly change its meaning. We can create new entries, but we
cannot remove an entry from the dictionary. What we can do is create new
entries that are better formulated and recommend that older items be
superseded by the new ones. There are a number of areas in the
dictionary where I hope that better data items will be defined someday.

   I have two sets of proposed additions to the dictionary, but before
we get started discussing them, I would like to ask that you please read
a draft of a chapter on pdCIF written for the International Tables
volume on CIF (volume G). I would appreciate comments, corrections and
questions. The chapter is 25 pages long and can be downloaded in
PostScript or PDF. (Upon request, I will mail a paper copy. I can also
supply it as a rather dense 9 page IT proof.)

   Here is where to get this chapter:

        http://www.iucr.org/~commit/itg/draft/23.ps  (PostScript)
        http://www.iucr.org/~commit/itg/draft/23.pdf (PDF)

   I also recommend that you make hard copy printouts of two documents,
the CIF Core dictionary and the pdCIF dictionary. You will probably not
want to read them (the pdCIF chapter alone should cure insomnia), but
you will likely need for reference periodically.  Note that the pdCIF
dictionary is an extension of the Core, so pdCIF is really the sum of
the two dictionaries. 

The Core dictionary can be downloaded from
        ftp://ftp.iucr.org/cifdics/cif_core_2.1.dic.ps (PostScript)
        ftp://ftp.iucr.org/cifdics/cif_core_2.1.dic.pdf (PDF)
        ftp://ftp.iucr.org/pub/cif_core.dic (ASCII)

and the powder dictionary can be downloaded from
        ftp://ftp.iucr.org/cifdics/cif_pd_1.0.ps (PostScript)
        ftp://ftp.iucr.org/cifdics/cif_pd_1.0.pdf (PDF)
        ftp://ftp.iucr.org/pub/cif_pd.dic (ASCII)

Here are some other useful links

 The CIF home page: http://www.iucr.org/iucr-top/cif/

 A Very Brief Introduction to CIF:
http://www.iucr.org/iucr-top/cif/powder-intro.html

 The pdDMG home page: http://www.iucr.org/iucr-top/lists/pddmg/

  My hope is that after reading the chapter, everyone will have a pretty
good idea of what is present in pdCIF and what is missing. 

Brian
 
********************************************************************
Brian H. Toby, Ph.D.                    Leader, Crystallography Team
Brian.Toby@NIST.gov      NIST Center for Neutron Research, Stop 8562
voice: 301-975-4297     National Institute of Standards & Technology
FAX: 301-921-9847                        Gaithersburg, MD 20899-8562
********************************************************************

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