[Ifeffit] Atoms 3.0beta7

Bruce Ravel ravel at phys.washington.edu
Thu Aug 15 11:02:02 CDT 2002

Hi folks,

I released a new version of Atoms today which includes one small (but
possibly important) change from the previous version.  I learned that
the database entry for a specific space group (I -4 3 d, #220) was in
error.  I fixed this and made a new release.  There is a new tarball
and Windows executable on my web site.  If you are a windows user, you
will also need to install the new version of the space_group.db file,
as per the instructions on the downloads page.  I also updated
WebAtoms on Matt's server.

This error has ABSOLUTELY NO IMPACT on any other space group.  Indeed,
without an atoms input file using the affected space group, you would
never notice the problem.

This underscores an interesting aspect of crystallography.  While
group theory tells us that there are 230 possible space group, nature
seems to prefer using only a small subset of them.  Indeed, in all the
years since I started working on Atoms, I have not seen an example of
a crystal in this space group until this week.  The collection of
input files that I distribute with Atoms for the purpose of testing
the code includes examples of less than 80 space groups.  Anyway, here
is the input file that lead me to the error in Atoms' space group data

   title = Cu3As Domeykite
   title = Iglesias, J. E., and Nowacki, W., 
   title = Zeitschrift fur kristallographie, kristallgeometrie, 
   title = kristallphysik, kristallchemie, v. 145, pp. 334-345 (1977).
   space = I -4 3 d
   a =	  9.6190
   core =	Cu	rmax =	  8.0
   ! elem   x          y          z
      Cu   -0.02930    0.12020    0.18760
      As   -0.02980   -0.02980   -0.02980

One might notice that the old Fortran version of Atoms handles this
input file correctly.  The irony of that is not lost on me,
particularly in light of my frequent and loud trumpeting of the
advantages of the new version over the old version.

Thanks to Elspeth Barnes for bringing this problem to my attention.


 Bruce Ravel  ----------------------------------- ravel at phys.washington.edu
 Code 6134, Building 3, Room 222
 Naval Research Laboratory                          phone: (1) 202 767 5947
 Washington DC 20375, USA                             fax: (1) 202 767 1697

 NRL Synchrotron Radiation Consortium (NRL-SRC)
 Beamlines X11a, X11b, X23b, X24c, U4b
 National Synchrotron Light Source
 Brookhaven National Laboratory, Upton, NY 11973

 My homepage:    http://feff.phys.washington.edu/~ravel 
 EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/

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