[Wien] supplement to EFG orientation divergence in supercell calculations

[Alexander Korthaus]

Dear Mr Blaha,

 

thank you for your quick response. Please correct me if I'm wrong, but
according to the efg2 paper by Cottenier and Koch one is supposed to
multiply the EFG Main Directions given in the Local Coordinate System by the
inverse Local Rotation Matrix from the struct file in order to get the Main
Directions in Wiens Global Coordinate System. If I do that for SG-139 for
the two Aluminum sites, it results in Vzz Main Directions parallel to c for
both sites. If I do the same procedure, for instance, for Atom Al1 in
SG-123, it results in a [0 1 0] direction for Vzz. The LRM from the struct
file for Al1 is [0 1 0;0 0 1;1 0 0]; the corresponding inverse LRM is [0 0
1;1 0 0;0 1 0]. This Matrix multiplied by the Vzz direction in the Local
Coordinate System, which is [1 0 0], yields the vector [0 1 0]. I always
thought that I was already done at this point and that the main directions
are comparable for both structures. Do I need to take an extra step and
consider the direction modifications from the outputs file in order to make
the MDs in the Global Coordinate System comparable?

 

I'm sorry that it's taking me so long to get it.

Thanks for your help,

best regards

Alex Korthaus

 


Subject: 

Re: [Wien] supplement to EFG orientation divergence in supercell
calculations


Date: 

Mon, 23 Feb 2015 18:09:01 +0100


From: 

Peter Blaha  <mailto:pblaha at theochem.tuwien.ac.at>
<pblaha at theochem.tuwien.ac.at>


Reply-To: 

A Mailing list for WIEN2k users  <mailto:wien at zeus.theochem.tuwien.ac.at>
<wien at zeus.theochem.tuwien.ac.at>


To: 

A Mailing list for WIEN2k users  <mailto:wien at zeus.theochem.tuwien.ac.at>
<wien at zeus.theochem.tuwien.ac.at>

 

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
toconsider for each site
the corresponding local rotatation matrix.
 
Check case.outputs (bottom), where it tells you also how the directions
aremodified 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
<mailto: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
(spacegroup123, 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
lastiteration 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 <mailto:pblaha at theochem.tuwien.ac.at> 
-----------------------------------------
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