[Pw_forum] U for Oxygen
Matteo Cococcioni
matteo at umn.edu
Thu Aug 6 17:15:09 CEST 2009
Dear Ali
ali kazempour wrote:
> Dear Matteo
> In your tutorial about LDA_U, you mentioned that the perturbation
> should be isolated. and said that we normally use supercell of
> increasing size up to when convergence of is reached. I don't
> understand how do you increase the size of the cell and how do you
> compute the U in larger supercell.? I mean how do you apply
> perturbation to bigger size or how to extrapolate the U to converge?
>
just like to the small one. please run the examples in the tutorial
> Another question according to prior email for computation of U by
> common method(not linear response) is : you mentioned that espresso
> cann't directly change the occupation of special orbital by hand, but
> it is possible to do by using constraint on total number of
> electron(total occupation) indirectly . Do you mean that( for example
> for Ti atom that has 2 electron in d orbital) ,what can i do is change
> the of number of nelup and neldw without change in nelec? or I have
> to do another switch? Would you please tell me in more details.
> Thank you very much for your aids
> Ali Kazempour
> Physics department, Isfahan University of Technology
> 84156 Isfahan, Iran. Tel-1: +98 311 391 3733
> Fax: +98 311 391 2376 Tel-2: +98 311 391 2375
>
> --- On *Tue, 8/4/09, Matteo Cococcioni /<matteo at umn.edu>/* wrote:
>
>
> From: Matteo Cococcioni <matteo at umn.edu>
> Subject: Re: [Pw_forum] U for Oxygen
> To: "PWSCF Forum" <pw_forum at pwscf.org>
> Date: Tuesday, August 4, 2009, 9:52 AM
>
>
> this is what comes out from the calculation (U(O) > U(Ni)).
> whether it's
> reasonable to apply U on O or not, I'm not sure.
>
> I think the U shouldn't be used on states that are completely
> occupied.
>
> Matteo
>
>
>
> ali kazempour wrote:
> > Dear Matteo
> > This means that hubbard parameter for oxygen is large (grater than
> > Ni). Is it correct or originate from another challenge?
> > thanks
> >
> > Ali Kazempour
> > Physics department, Isfahan University of Technology
> > 84156 Isfahan, Iran. Tel-1: +98 311 391 3733
> > Fax: +98 311 391 2376 Tel-2: +98 311 391 2375
> >
> > --- On *Tue, 8/4/09, Matteo Cococcioni /<matteo at umn.edu
> </mc/compose?to=matteo at umn.edu>>/* wrote:
> >
> >
> > From: Matteo Cococcioni <matteo at umn.edu
> </mc/compose?to=matteo at umn.edu>>
> > Subject: Re: [Pw_forum] U for Oxygen
> > To: "PWSCF Forum" <pw_forum at pwscf.org
> </mc/compose?to=pw_forum at pwscf.org>>
> > Date: Tuesday, August 4, 2009, 6:59 AM
> >
> >
> >
> > Dear Ali,
> >
> >
> >
> > ali kazempour wrote:
> > > Dear Matteo
> > > I used your comment and followed your example for NiO and I
> > succeed
> > > to get U for TiO2. But in file Ur16.out I see three column .
> > >
> >
> > I don't have any three column section in any of my files. so if
> > you want
> > me to help you you have to report at least a section of your
> output
> > file. This is a good habit actually in consideration of the
> fact that
> > this is not a private conversation (I would have asked you
> in any
> > case
> > as I don't remember by heart the format of any file) between me
> > and you
> > but a message to the forum and you want other people to
> understand
> > what you are saying.
> >
> > > The first is number of atom in supercell , second is U
> value for Ni
> > > atom and I don,t know the third? does the third belong
> to U value
> > > for Oxygen or not? Because the third column kas big value?
> > >
> > >
> > > another question is for isolated atom Hubbard parameter.
> What do
> > you
> > > expect about the value of U for Isolated atom? Is this big
> value
> > > (greater than 10 eV) or it would be tiny value?
> > >
> >
> > I think it will be meaningless for the reasons I explained
> in my last
> > email. To obtain a meaningful number for the isolated atom you
> > probably
> > have to abandon the idea to use a perturbation in the
> potential and
> > change instead the number of electrons directly. This means
> you will
> > have to do calculations on atoms having fractional charges which
> > requires additional corrections if you use a code designed for
> > periodic
> > systems (crystals). However I have never done this isolated atom
> > calculation of U before so I don't have more details about it.
> > I see (from a private email) you are thinking of computing U
> for the
> > isolated atom and to obtain a value for the crystal just by
> > dividing by
> > the epsilon_inft. the method is proposed in
> >
> > http://link.aps.org/doi/10.1103/PhysRevB.74.045202
> >
> > (which I haven't re-read yet).
> >
> > I see a couple of problems:
> >
> > 1) (not important for ZnO). suppose you have Fe3O4 with Fe2+ and
> > Fe3+.
> > these Fe ions likely have different U. how do you obtain
> > a different number from the atomic code? would you do the
> calculation
> > for isolated Fe2+ and Fe3+?
> >
> > 2) how do you get epsilon? since it's a linear response
> property I
> > don't
> > think its calculation is any cheaper than the direct
> calculation of U.
> >
> > regards,
> >
> > Matteo
> >
> > > should we choose for running the script for isolated atom only
> > gamma
> > > point or we have to choose a fine mesh?
> > > thanks a lot
> > >
> > >
> > > Ali Kazempour
> > > Physics department, Isfahan University of Technology
> > > 84156 Isfahan, Iran. Tel-1: +98 311 391 3733
> > > Fax: +98 311 391 2376 Tel-2: +98 311 391 2375
> > >
> > > --- On *Sun, 8/2/09, Matteo Cococcioni /<matteo at umn.edu
> </mc/compose?to=matteo at umn.edu>
> > </mc/compose?to=matteo at umn.edu
> </mc/compose?to=matteo at umn.edu>>>/* wrote:
> > >
> > >
> > > From: Matteo Cococcioni <matteo at umn.edu
> </mc/compose?to=matteo at umn.edu>
> > </mc/compose?to=matteo at umn.edu </mc/compose?to=matteo at umn.edu>>>
> > > Subject: Re: [Pw_forum] occupation
> > > To: "PWSCF Forum" <pw_forum at pwscf.org
> </mc/compose?to=pw_forum at pwscf.org>
> > </mc/compose?to=pw_forum at pwscf.org
> </mc/compose?to=pw_forum at pwscf.org>>>
> > > Date: Sunday, August 2, 2009, 8:31 AM
> > >
> > >
> > > Dear Ali,
> > >
> > > 1, -1, 0 are just spin indexes to tell the code what
> is the
> > relative
> > > magnetization of the atoms (parallel, antiparallel, or
> none). if
> > > your system is non magnetic put all 0. or set magn =
> .false.
> > and put
> > > nothing.
> > > you should look at the examples on Fe and Si as well and
> > learn from
> > > there by comparison.
> > >
> > > Matteo
> > >
> > >
> > >
> >
> >
> > --
> > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> > Matteo Cococcioni
> > Department of Chemical Engineering and Materials Science,
> > University of Minnesota
> > 421 Washington Av. SE
> > Minneapolis, MN 55455
> > Tel. +1 612 624 9056 Fax +1 612 626 7246
> > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> >
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> >
> >
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> --
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> Matteo Cococcioni
> Department of Chemical Engineering and Materials Science,
> University of Minnesota
> 421 Washington Av. SE
> Minneapolis, MN 55455
> Tel. +1 612 624 9056 Fax +1 612 626 7246
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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--
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Matteo Cococcioni
Department of Chemical Engineering and Materials Science,
University of Minnesota
421 Washington Av. SE
Minneapolis, MN 55455
Tel. +1 612 624 9056 Fax +1 612 626 7246
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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