[ase-users] Bug in spacegroup 154

[Maxime van den Bossche]

Hello!

I came across a bug when trying to read in the following
quartz SiO2 structure (in CIF format), which belongs
to the P 32 2 1 spacegroup (number 154).

http://rruff.geo.arizona.edu/AMS/CIF_text_files/00859_cif.txt

The number of atoms, as well as atomic positions in the resulting
Atoms object are incorrect, and it seems to be due to errors in
the way the spacegroup's symmetry operations are defined.

The last three lines in the "symmetry operations" block
of the entry 154 in /ase/lattice/spacegroup/spacegroup.dat
are as follows:

    0  1  0     1  0  0     0  0 -1    0.0000000000  0.0000000000  0.0000000000
    1 -1  0     0 -1  0     0  0 -1    0.0000000000  0.0000000000  0.3333333333
   -1  0  0    -1  1  0     0  0 -1    0.0000000000  0.0000000000  0.6666666667

but the symmetry translations should be corrected to:

    0  1  0     1  0  0     0  0 -1    0.0000000000  0.0000000000  0.6666666667
    1 -1  0     0 -1  0     0  0 -1    0.0000000000  0.0000000000  0.0000000000
   -1  0  0    -1  1  0     0  0 -1    0.0000000000  0.0000000000  0.3333333333

After this fix, I got the quartz structure I expected.

Regards,
Maxime

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