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Re: CoreCIF revision 2.3 _refine_ls_extinction_method:

  • To: Multiple recipients of list <coredmg@iucr.org>
  • Subject: Re: CoreCIF revision 2.3 _refine_ls_extinction_method:
  • From: Howard Flack <Howard.Flack@cryst.unige.ch>
  • Date: Fri, 27 Jun 2003 10:49:16 +0100 (BST)

The truth of the matter is that extinction parameters are junk.
Junk*10**5 is just the same amount of junk. Also 'tidy junk' is more
junky than 'untidy junk' because the neatness tempts you to believe that
there is some true order or meaning. There is no decent routine physical
experiment that one can do on a crystal that depends on the same things
which are critical to extinction. You hence have no way of knowing
whether the values of the parameters of an extinction model are
reasonable for the crystal under study.

My recommendation is to stop any further discussion within CoreDmg on
extinction parameters whilst awaiting a significant theoretical or
experimental breakthrough.


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