[Wien] Open core treatment for 4f insulators

[Laurence Marks]

Open core puts the 4f into the core as spherically symmetric wavefunctions
(with spin orbit). Therefore it will get you a reference state, but it will
not give you the crystal field splitting.

To get the splitting you have to use LDA+U (which I don't trust for 4f) or
on-site hybrid (better).

N.B.,
1) Has your calculation converged?
2) Did you correctly alter the number of atoms -- i.e. grep :NEC *.scf?
3) Are you running spin polarized with correct case.incup/dn (which does
not seem to be described in the FAQ)? I would not trust a non spin
polarized calculation much.
4) Have you run a number of other cases first to learn? This is not
trivial, I would suggest running more than TiC first, for instance NiO and
some others.

_____
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu

On Tue, Nov 5, 2019, 07:36 Abhijit B K <bk.abhijit1 at gmail.com> wrote:

> Dear Wien2k users,
>
> I am a beginner for WIEN2k or any kind of DFT calculations. I am trying to
> follow the formalism by Pavel Novak to calculate the *crystal field
> parameters* of a rare earth oxide insulator. I am stuck in the first step
> i.e *open core treatment*. I follow all the steps mentioned in the manual
> as well as FAQ and I don't sift the k-mesh. What I see in the .scf file is
> *metallic behavior instead of insulator. *i.e
>
> :GAP (global)   :    0.0    Ry =     0.0   eV (metal)
> I understand this as a product  of screening.
>
> Can someone suggest some ways to achieve a* non zero gap*?
> I wouldn't want to use LDA+U.
>
> Best wishes,
>
> Abhijit
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