[Wien] EFG orientation divergence in supercell calculations

[Alexander Korthaus]

Dear colleagues,

 

I'm having a problem calculating the absolute EFG tensor orientations of
BaAl4 in its original structure (spacegroup 139), a supercell (spacegroup
123, a' = 2a) and in its original structure with no symmetry (P1). While the
resulting EFG orientations are comparable and seem to make sense for the
original structure and the equivalent cell in P1, EFG orientations obtained
from supercell calculations turn out to point in quite different directions.
In SG-139 Vzz points along the crystallographic c-axis for both of the two
inequivalent Aluminum sites. In SG-123 however, two different orientations
of Vzz are found for the Aluminum atoms, one pointing along and one
perpendicular to the c-axis. I've experienced this behaviour for quite a few
different structures and lattices besides BaAl4. It is always the supercell
calclulations showing the ,wrong' EFG directions. I attached two files to
this email, each showing the last iteration step from the scf file for the
original structure (SG_139.txt) and the superstructure (SG_123.txt). I would
appreciate it a lot if anyone could help me figure out what I'm doing wrong.

 

Thanks in advance,

best regards,

Alex Korthaus

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