[Pw_forum] Does considering 2*2*2 supercell is required while calculating LR U

[SRKC Sharma Yamijala]

Dear Dr. Matteo,

Thanks a lot. It indeed helped me. May I ask you few more things.

1. Which 'U', among the two ways, I need to consider (for example, for my
DMFT calculations) for the TM atom?
        (a) U obtained by considering Hubbard_alpha only for the TM atom
        (b) U obtained by considering Hubbard_alpha on both TM atom and O
atom.
2. Why we need to shift the atoms to origin always?
3. Can we calculate the onsite J using the QE?
4. Are there any tutorials for calculating DFT+U+V (which you have
described in the last parts of chapter 4 in the book Correlated electrons:
>From Models to Materials)?

Thanks a lot for your help and support,
Sincerely,
Sharma.

*******************************************************
*Chaitanya Sharma,*
*Prof. Pati'*s group,
Chemistry and Physics Materials unit,
JNCASR, BANGLORE,
Lab:: (080-2208) 2581, 2809
https://sites.google.com/site/sharmasrkcyamijala/
*********************************************************

On Tue, Nov 18, 2014 at 11:41 PM, SRKC Sharma Yamijala <
sharmajncasr at gmail.com> wrote:

> Dear PW members,
>
> I have gone through the tutorials of LDA+U available online (mainly of
> Matteo Cococcioni and also his PRB 2005 paper). I am interested in
> calculating the U for the system SrVO3 and others. If I correctly follow
> the tutorial on NiO, to calculate U, I need calculate the scf with 2*2*2
> supercell (and with 4*4*4 etc. till U convergence) by keeping Ni at the
> origin once and by keeping O at the origin next. If I follow the above and
> consider the 2*2*2 supercell then the number of atoms in my system will be
> 40.
>
> But, I am guessing (I may be wrong) that supercell is considered because
> of the AFM nature of NiO ground state. So, can someone please clarify
> whether considering supercell is required for non-magnetic/Ferro-magnetic
> systems also or not?
>
> Thanking you for your support,
> Sincerely,
> Sharma.
> ********************************************************
> *Chaitanya Sharma,*
> *Prof. Pati'*s group,
> Chemistry and Physics Materials unit,
> JNCASR, BANGLORE,
> Lab:: (080-2208) 2581, 2809
> https://sites.google.com/site/sharmasrkcyamijala/
> *********************************************************
>
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