[Wien] Error while doing AFM calculation

[Laurence Marks]

As Peter said, your structure is certainly wrong. There is a method already
in Wien2k to help avoid this type of problem for oxides. After running "x
nn" or "setrmt" you do "grep Bond *.outputnn". This will give you the bond
valence sums (see https://en.wikipedia.org/wiki/Bond_valence_method), which
should be close to the nominal valence, within 10-20%. When I look at your
structure the values for the Na & Yb are about right, but the O is really
wrong (6.77 when it should be 1.8-2.2).

If you want to go further you should read Pauling's rules (
https://en.wikipedia.org/wiki/Pauling%27s_rules). While these may be old,
they remain valid. In 99.9% of cases if an oxide (and many others) violate
Pauling's rules and the bond valences are odd they are high energy. This is
known for the bulk, and also works for surfaces
(DOI: 10.1016/j.surfrep.2018.08.001) and I expect other defects.

Once you have a reasonable structure the RMT for the Yb will be much
larger, the bond valences more reasonable and the problem in lapw1 will
probably go away.

On Wed, May 19, 2021 at 2:41 AM Peter Blaha <pblaha at theochem.tuwien.ac.at>
wrote:

> No, your struct file is certainly not correct.
>
>  From the header I can see you want to do   NaYbO2
>
> So look into your struct file:
>
> I see 4 atoms, but a stoichiometry of   Na Yb4 O2  ???
>
> Of course, also your RMTs are completely unphysical and the atoms are
> much too close.
>
> If one removes the 3rd atom (Y2 with 3 equ. atoms), the structure might
> be ok ?   However, with one Y atom/cell, you cannot make a AFM
> structure, only a FM one. You need to know how the AFM structure is and
> then make a corresponding supercell.
>
> --
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu
"Research is to see what everybody else has seen, and to think what nobody
else has thought" Albert Szent-Györgyi
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