[Wien] The problem for atomic forces in the supercells of lanthanides compounds

[Laurence Marks]

Some comments:
a) 99.999% probability that you messed something up when you created the
supercell, or you have FOR in case.in2(c) in one case and not the other.
b) Putting 4f into the core is at best dubious. What valence are you using,
for instance Ce4+, Ce3+ or Ce0+ ? You are deciding what the electronic
structure is. While you might be right,....
c) -eece, as I find +U to be dubious for 4f.

On Fri, Sep 3, 2021 at 10:40 AM Artem Tarasov <artem.tarasov at spbu.ru> wrote:

> Dear wien2k users,
>
> Recently, I have noticed a strange problem related to the forces
> inside the supercell for compounds containing 4f-atoms with 4f-states
> placed on the core level ("open core approximation" for Tb, Dy, Ho, Ce
> etc.). If we relax the slab of a cell with a period of 1x1 and a
> symmetry group of P4mm, and then make a cell with a doubled lateral
> period of 2x2 from the relaxed structure, then after converging the
> density for the 2x2 cell the forces on all atoms in the supercell grow
> significantly compared to the case of the 1x1 cell. Up to a jump from
> 0.05 to 68 mRy/bohr on individual atoms. I thought that the problem
> may be related to the shift of the k-grid, because when I move to the
> supercell, I change the k-grid from 12x12 to 6x6, and I had supposed
> that such a k-grid may not be enough for an accurate calculation.
> However, even if I don't use the k-grid shift in both cases, this
> problem persists. My calculation is a slab of CeB6 with symmetry P4mm
> with Ce4f states given in case. inc as
>
> 16 0.70  0  NUMBER OF ORBITALS (EXCLUDING SPIN), SHIFT, IPRINT
> …
> 4, 3,0.43               ( N,KAPPA,OCCUP)
> 4,-4,0.57               ( N,KAPPA,OCCUP)
>
> Thank you in advance for your help.
>
> Best regards,
> Artem Tarasov
> Department of Solid State Electronics
> Saint Petersburg University
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-- 
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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