[Wien] Order of equivalent positions in case.struct

[Fecher, Gerhard]

Hallo Lukasz,
If you edit the structure (or create a new one)  and use sgroup afterwards then it will resort the equivalent sites again when you accept the structure.
If the space group was already ok, then you do not need to accept changes made by sgroup.
I do not know whether there exists an IUCr recommendation how the equivalent positions should be ordered crystallographically. However, it should not affect the electronic structure.

I am not sure what you looking for, but how can two equivalent atoms contribute different to the electronic structure.
For example, if the spin densities at two sites are different then they can not be equivalent.

Ciao
Gerhard

DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
"I think the problem, to be quite honest with you,
is that you have never actually known what the question is."

====================================
Dr. Gerhard H. Fecher
Institut of Physics
Johannes Gutenberg - University
55099 Mainz
________________________________________
Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Peter Blaha [peter.blaha at tuwien.ac.at]
Gesendet: Samstag, 31. August 2024 19:15
An: wien at zeus.theochem.tuwien.ac.at
Betreff: Re: [Wien] Order of equivalent positions in case.struct

Of course you can edit the struct file and exchange the order of
equivalent positions.

Am 29.08.2024 um 13:41 schrieb pluto via Wien:
> Dear Prof. Blaha, dear All,
>
> WIEN2k automatically detects equivalent positions (from symmetries) to
> allow faster calculations. In the slab geometry typically there are (at
> least) two equivalent positions, at the top and at the bottom of the slab.
>
> QTL is able to provide band characters for the first of the equivalent
> positions. This is very convenient because one can check e.g.
> spin-polarization of Rashba-type surface states without disconnecting
> the atoms (which would be expensive). Regular x lapw2 -band will average
> over the equivalent positions, therefore typically canceling any "hidden
> spin polarization".
>
> However, WIEN2k choses the first equivalent position automatically. This
> means that sometimes it can be at the top of the slab, and sometimes at
> the bottom of the slab (say surface layer is at the top and subsurface
> layer at the bottom of the slab).
>
> Is there a way to control which positions is the first equivalent
> position? Can I manually edit case.struct file and change the order of
> the equivalent positions?
>
> Best,
> Lukasz
>
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--
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Peter Blaha,  Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
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