[Wien] supplement to EFG orientation divergence in supercell calculations

[Peter Blaha]

I guess you gave the answer yourself !

In SG 193 the local rotation matrices are always leaving the z axis along the crystallographic c axis.

In SG 123, however, you have different loc.rots, which interchange x and z. Thus some of the EFGs
point into the local x-direction, which is the global z anyway. You need to consider for each site
the corresponding local rotatation matrix.

Check case.outputs (bottom), where it tells you also how the directions are modified because of some
highest symmetry element showing into x.

Am 23.02.2015 um 17:02 schrieb Alexander Korthaus:
> I forgot to include the struct files. EFG orientations do not make a lot of sense without the corresponding Local Rotation Matrices.
>
> Regards,
>
> A. Korthaus
>
> *Von:*Alexander Korthaus [mailto:alexander.korthaus at ac.rwth-aachen.de]
> *Gesendet:* Montag, 23. Februar 2015 16:16
> *An:* 'Wien at zeus.theochem.tuwien.ac.at'
> *Betreff:* EFG orientation divergence in supercell calculations
>
> 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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-- 
-----------------------------------------
Peter Blaha
Inst. Materials Chemistry, TU Vienna
Getreidemarkt 9, A-1060 Vienna, Austria
Tel: +43-1-5880115671
Fax: +43-1-5880115698
email: pblaha at theochem.tuwien.ac.at
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