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

[Matteo Cococcioni]

On Tue, Nov 18, 2014 at 7:11 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?
>
>

Dear Sharma,

NiO needs a unit cell of 4 atoms becaus it is AFM. if it was FM it would be
possible to use a cell of 2 atoms only. In both cases you would need to
perform the linear response calculation of U in a supercell (of the
appropriate cell).

Hope this helps

Matteo




> 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/
> *********************************************************
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20141119/febfe6f9/attachment.html>