[Wien] MBJ fails to produce gap unto 0.6 for VO2 M1 phase

[Tran, Fabien]

Probably yes and I think that this particular example of VO2 can be used as a very good one to illustrate the concept of density-driven error introduced by Burke:

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111.073003<https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111.07300$>


No, this is not possible to calculate forces by using mBJ as a potential. The forces have no meaning when they are calculated with a potential that is not a functional derivative.



________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Xavier Rocquefelte <xavier.rocquefelte at univ-rennes1.fr>
Sent: Wednesday, May 13, 2020 9:08 AM
To: wien at zeus.theochem.tuwien.ac.at
Subject: Re: [Wien] MBJ fails to produce gap unto 0.6 for VO2 M1 phase


Thank you Fabien for your comment.

I was not thinking that the energy can be used in mBJ. It remains qualitative and not quantitative I imagine, because we cannot optimize the geometry with mBJ. Thus these mBJ in the table can be viewed as pertubation of the LDA ones, which are not self-consistent. Is it the idea?




Le 13/05/2020 à 08:50, Tran, Fabien a écrit :

Regarding the mBJLDA results in Table I of PRB 86, 075149 (2012), they are incorrect as Xavier wrote. By default, the LDA energy is used with mBJLDA potential. So, these results in Table I correspond to the LDA functional evaluated with the mBJLDA orbitals. In some sense they are interesting since they show that the LDA functional can provide correct trends provided that better orbitals are used.


________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at><mailto:wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Xavier Rocquefelte <xavier.rocquefelte at univ-rennes1.fr><mailto:xavier.rocquefelte at univ-rennes1.fr>
Sent: Wednesday, May 13, 2020 7:47 AM
To: wien at zeus.theochem.tuwien.ac.at<mailto:wien at zeus.theochem.tuwien.ac.at>
Subject: Re: [Wien] MBJ fails to produce gap unto 0.6 for VO2 M1 phase


Just one comment about this paper. They compare total energies obtained from mBJLDA.

However, mBJ is not self-consistent with respect to the total energy. mBJ is a semilocal potential.

Thus Tables I and II contain errors.

Best wishes

Xavier

Le 13/05/2020 à 05:59, Wasim Raja Mondal a écrit :
Dear All,
            Sorry for my email. MBJ works for this material also.
Please see the reference if anybody interested: PHYSICAL REVIEW B 86, 075149 (2012)

Thanks
Wasim

On Tue, May 12, 2020 at 2:02 AM Xavier Rocquefelte <xavier.rocquefelte at univ-rennes1.fr<mailto:xavier.rocquefelte at univ-rennes1.fr>> wrote:

Dear Wasim,

In VO2, vanadium is 4+ and thus we expect one electron in V(3d) states, thus a gap based on d-d transitions.

MBJ alone is not expected to open the gap. You will need to put a Hubbard term at least.

I recommend you to read the following article which deals with DFT+DMFT and M1 phase of VO2.

Phys. Rev. Lett. 117, 056402 (2016)

Best regards

Xavier

Le 12/05/2020 à 03:09, Wasim Raja Mondal a écrit :
Dear Experts,
                     I am doing some calculations for VO2 M1 phase. To get the correct band gap value, I applied MBJ. But, I am getting zero gap. To get the gap, I increased the c value. with such large c value, there is no sign of convergence of my calculation.

I appreciate if experts have any comments and suggestions.

Regards
Wasim



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