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 > > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% > > > > _______________________________________________ > > Pw_forum mailing list > > 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>> > > http://www.democritos.it/mailman/listinfo/pw_forum > > > > > > > ------------------------------------------------------------------------ > > > > _______________________________________________ > > Pw_forum mailing list > > Pw_forum at pwscf.org </mc/compose?to=Pw_forum at pwscf.org> > > http://www.democritos.it/mailman/listinfo/pw_forum > > > > > -- > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% > 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 > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org </mc/compose?to=Pw_forum at pwscf.org> > http://www.democritos.it/mailman/listinfo/pw_forum > > > ------------------------------------------------------------------------ > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 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 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
