Crystallography Online: the website of the International Union of Crystallography

The notice below announces the preparation of a CIF dictionary for 
reflectivity data.  Part of COMCIFS' mandate is to ensure that 
information about new dictionaries is widely disseminated so that anyone 
with an interest in the topic can participate.  Please pass this message 
on to anyone who may be interested.

David Brown
Chair of COMCIFS

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 A Crystallographic Information File for Specular Reflectivity Data

 A. van der Lee, Institut Europeen des Membranes, Montpellier, France and
 I. D. Brown, Chair of COMCIFS.  Brockhouse Institute for Materials
 Research, McMaster University, Hamilton, Ont. Canada.  idbrown at mcmaster.ca


 Since the early nineties X-ray and neutron specular reflectivity have
 been the scattering techniques of choice for materials scientists who
 want to study the vertical density profile of thin films, whether
crystalline,
 amorphous or liquid.  Important structural
 parameters, such as the electronic or nuclear density, the thickness, and
 the interfacial roughness of thin layers, can be deduced from specular
 reflectivity data using more or less straightforward modelling
 techniques (1).  Although initially developed by physicists, the
 technique is now used by chemists and biologists,
 each however tends to speak their own reflectivity language.
 This has led to a large variety of ways in which
 results from specular reflectivity experiments
 are presented, making reflectivity papers sometimes rather difficult to
 read, even for specialists in the field.

 Some of us working in the field have thought it worthwhile to
 standardize the terminology by defining a Crystallographic Information
 Framework (CIF) Dictionary for specular reflectivity data. The benefits
 provided by CIF for single-crystal diffractometry are well known (2),
 and the CIF developed for powder diffraction (pdCIF, 3) has become more
 popular with the development of CIF-exporting modules in programs such
 as GSAS (4).  In view of these developments it is expected that a CIF
 for specular reflectivity data (rfCIF) could make it easier to exchange
 specular reflectivity measurements between researchers working in
 different or multidisciplinary fields.  It would also simplify archiving
 and interpreting this information.

 An informal working group of specialists worldwide has recently
 been formed to produce a reflectivity CIF dictionary (rfCIF).  A draft
 version of the dictionary is being prepared in collaboration with
 COMCIFS, the committee that oversees the CIF project for the
 International Union of Crystallography.  A number of practitioners in
 the field have already commented on a first draft of the dictionary and
 any one else with an interest in this project is invited to contact
one of the  members of the working group listed below:

A. van der Lee (chair) University of Montpellier, France.
 <http://www.iemm.univ-montp2.fr/xrayweb/main_uk.html> click on "Contacts".

E. Bontempi, University of Brescia, Italy

D. Chateigner, CRISMAT-ENSICAEN, France

P.F. Fewster, PANalytical Research Centre, England

B. Harzallah,  University of Monastir, Tunisia

P. Kienzle, NIST, USA

K. Sakurai,  University of Tsukuba, Japan

A. Ulyanenkov, Bruker AXS, Karlsruhe, Germany.


 REFERENCES

 (1) see e.g. J. R. Lu, E. M. Lee and R. K. Thomas, Acta Cryst. (1996).
 A52, 11-41

 (2) International Tables for Crystallography Volume G: Definition and
exchange
of crystallographic data,  Eds.  S. Hall and B. McMahon, Springer.

 (3) B. H. Toby and N. Ashcroft, Acta Cryst. (2005). A61, C483

 (4) B. H. Toby, R. B. Von Dreele and A. C. Larson, J. Appl. Cryst.
 (2003). 36, 1290-1294
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