[Wien] Bader charge

[leila mollabashi]

Dear Wien2k developers and users,

I would like to calculate Bader charges in BaTiO3. The input and output
files are uploaded to
https://www.mediafire.com/file/o6ceodngk93mh72/aim.rar/file for your kind
consideration.

I have run a PBE-GGA calculation using 1000 k-points, RMTKmax =7, Gmax = 12
(Bohr)-1 employing WIIEN2k_21.1 and then executed “x aim” by the third part
of case.inaim from SRC_templates. The calculated charges are:

Ba: 2.91, Ti: 2.68, O: 0.299

The results cannot satisfy the stoichiometry of the compound because of the
positive charge wrongly calculated for O, i.e., 2.91+2.68+3*0.299=6.487 !=
0

Then, to improve the results, I increased the LM in the original
calculation with no optimistic effect.

Accidently, I found that the Bader charges of BaTiO3 can be perfectly
improved using “x aim” of WIIEN2k_18.2 as follows:

Ba: 1.52, Ti: 2.23, O: -1.25

The above results, as calculated by the older version 18.2, not only give a
negative value for the charge of oxygen but also perfectly lead to zero
taking the stoichiometry of the compound into account, i.e.,
1.52+2.23+3*(-1.25) = 0.

For sure, I checked the 14 and 16.1 versions of the WIEN2k code and found
correct results the same as WIIEN2k_18.2. This shows that most likely
something is different in the older versions WIIEN2k_18.2, WIIEN2k_16.1,
and WIIEN2k_14 compared to the latest version WIIEN2k_21.1?

I also checked LaCrO3, and found the same dissonancy. The Bader charges
were calculated for LaCrO3 to be La: 2.08, Cr: 1.65, O:  -1.24  in Ref.
[Energy Environ. Sci., 2011, 4, 4933]. These results also correctly lead to
zero approximately: 2.08+1.65+3*(-1.24) ~ 0.01.

Would you, please, have a look at this issue and let us know the source of
the above discrepancy?

Sincerely yours,

Leila Mollabashi
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