[Wien] OK: Change of structure symmetry

Wed Oct 19 19:01:20 CEST 2016

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________________________________
De: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> en nombre de Tomas Kana <kana at seznam.cz>
Enviado: miércoles, 19 de octubre de 2016 06:49:34 a. m.
Para: A Mailing list for WIEN2k users
Asunto: [Wien] OK: Change of structure symmetry

Dear Pablo,

Thank you for explaining your point. Now I understand.

With best regards

Tomas

PS: No, I am not a hockey player :o)

Dear Tomas

Are you a hokey player? I suppose not!

The problem with this is that the cell goes from CXY to P then in the cell the number of atoms doubles.

What I did is to see the positions of the changes of the atoms with sgroup

Before sgroup:

 1: X=0.50000000 Y=0.00000000 Z=0.63000000
 2: X=0.00000000 Y=0.00000000 Z=0.63000000
 3: X=0.50000000 Y=0.25000000 Z=0.38122315
 3: X=0.50000000 Y=0.75000000 Z=0.38122315
 4: X=0.50000000 Y=0.25000000 Z=0.87877685
 4: X=0.50000000 Y=0.75000000 Z=0.87877685
 5: X=0.75000000 Y=0.00000000 Z=0.35739347
 5: X=0.25000000 Y=0.00000000 Z=0.35739347
................
16: X=0.50000000 Y=0.75000000 Z=0.73290499
17: X=0.25000000 Y=0.34304549 Z=0.35413297
17: X=0.75000000 Y=0.65695451 Z=0.35413297
17: X=0.75000000 Y=0.34304549 Z=0.35413297
17: X=0.25000000 Y=0.65695451 Z=0.35413297
18: X=0.75000000 Y=0.15695450 Z=0.90586703
=============

After sgroup

 1: X=0.63000000 Y=0.63000000 Z=0.50000000
 2: X=0.63000000 Y=0.63000000 Z=0.00000000
 3: X=0.63122315 Y=0.38122315 Z=0.00000000
 4: X=0.63122315 Y=0.38122315 Z=0.50000000
 5: X=0.12877685 Y=0.87877685 Z=0.00000000
 6: X=0.12877685 Y=0.87877685 Z=0.50000000
 7: X=0.35739347 Y=0.35739347 Z=0.25000000
 7:X= 0.35739347 Y=0.35739347 Z=0.75000000
.............................
20: X=0.98290499 Y=0.73290499 Z=0.50000000
21: X=0.51108748 Y=0.35413297 Z=0.25000000
21:X= 0.51108748 Y=0.35413297 Z=0.75000000
22: X=0.69717846 Y=0.35413297 Z=0.25000000
22:X= 0.69717846 Y=0.35413297 Z=0.75000000
23: X=0.74891253 Y=0.90586703 Z=0.25000000
================

As you can see

a=>c

b+c=>a

c=>b

then you can see how the atoms split, for example

atoms '3' split into '3' and '4'

atoms '17' split into '21' and '22'

one have to take into account that the original structure is

CXY and a,b are equivalent to a+.5,b+.5

The b+c=>a is the consequence of the 90 => 135 degrees

I would be easy to make a program to change 135 => 90

Thank for your comments

             Pablo

________________________________
De: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> en nombre de Tomas Kana <kana at seznam.cz>
Enviado: viernes, 14 de octubre de 2016 05:24:55 a. m.
Para: A Mailing list for WIEN2k users
Asunto: Re: [Wien] Change of structure symmetry

Dear Pablo,
I tried to play with your structure and I succeeded.
First,  run
x supercell
always one cell in x- y- and z- directions
zero shift in all directions
 Enter your  target lattice type:
P
(you must choose primitive lattice in order to break
the symmetries you do not want there).
Zero vacuum in all directions.
Then
cp TiO2-sup_super.struct TiO2-sup.struct
Edit the TiO2-sup.struct file and find the two Cu atoms.
Rewrite the space after first Cu to 1.
Rewrite the space after second Cu to 2.
Or do these two things comfortably using w2web.
You must have them inequivalent.
By the way, are you sure that the vacuum you have for your slab is
sufficient? When I use slabs I try to have vacuum around 20 bohrs.
Then  run
x sgroup
By checking TiO2-sup.outputsgroup you see that sgroup has chosen
monoclinic lattice but with all three angles equal to 90 degrees.
(Space group 56  6 Pm)
Then, I STRONGLY RECOMMEND TO ERASE ONE OF THE Cu ATOMS,
probably the one at the position 0 0 0.
It worked on my computer.
HTH
Tomas
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