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Banning DIFABS (A Summary from circa 1st July 1994)

A discussion on whether the absorption correction software, DIFABS, should be banned, was started on April 20th by Tom Spek on the newsgroup sci.techniques.xtallography and seems to have reached compatable conclusions. It is hoped a agreed summary can be generated and submitted to an appropriate journal.

The aims of a journal article would be to raise awareness of both the potential applications of this newsgroup, and the DIFABS issue.

There is concern over the use and misuse of absorption correction software such as DIFABS to determine crystal structures. Via discussion, this has resulted in the following actions and conclusions :-

More emphasis, if possible, on "customers" providing journal quality crystals for analysis. Where this is not practical, data-collection strategies can be altered to accomodate the crystal at hand. i.e.:- Use of such correction software should be explicitly stated with the following submitted :- [which are recommended - 1 or all?] Methods for the easy, safe checking and alignment of single crystal diffractometers are available and possible with even home made equipment. For instance, using equipment such as cheap hand lasers, it is potentally a trivial and safe job to check that the X-ray beam is bathing the entire crystal. Routine checking of equipment should be encouraged to minimize the collection of poor quality data. Thus minimizing concerns about the abuse of absorption correction software to correct for systematic errors caused by poor alignment and/or partial irradiation of the crystal.

A "round robin" comparing the effects of "various?" absorption correction software vs uncorrected results would be very beneficial.


 
Lachlan Cranswick  -  CSIRO     _--_|\  lachlan@dmp.CSIRO.AU 
Division of Mineral Products   /      \ tel +61 3 647 0367 
PO Box 124, Port Melbourne     \_.--._/ fax +61 3 646 3223 
3207 AUSTRALIA    


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