<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Dear Matteo<br>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?<br>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.<br>Thank you very much for your aids<br>Ali Kazempour<br>
Physics department, Isfahan University of Technology<br>
84156 Isfahan, Iran. Tel-1: +98 311 391 3733<br>
Fax: +98 311 391 2376 Tel-2: +98 311 391 2375<br><br>--- On <b>Tue, 8/4/09, Matteo Cococcioni <i><matteo@umn.edu></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>From: Matteo Cococcioni <matteo@umn.edu><br>Subject: Re: [Pw_forum] U for Oxygen<br>To: "PWSCF Forum" <pw_forum@pwscf.org><br>Date: Tuesday, August 4, 2009, 9:52 AM<br><br><div class="plainMail"><br>this is what comes out from the calculation (U(O) > U(Ni)). whether it's <br>reasonable to apply U on O or not, I'm not sure.<br><br>I think the U shouldn't be used on states that are completely occupied.<br><br>Matteo<br><br><br><br>ali kazempour wrote:<br>> Dear Matteo<br>> This means that hubbard parameter for oxygen is large (grater than <br>> Ni). Is it correct or originate from another challenge?<br>> thanks<br>><br>> Ali Kazempour<br>> Physics department, Isfahan University
of Technology<br>> 84156 Isfahan, Iran. Tel-1: +98 311 391 3733<br>> Fax: +98 311 391 2376 Tel-2: +98 311 391 2375<br>><br>> --- On *Tue, 8/4/09, Matteo Cococcioni /<<a ymailto="mailto:matteo@umn.edu" href="/mc/compose?to=matteo@umn.edu">matteo@umn.edu</a>>/* wrote:<br>><br>><br>> From: Matteo Cococcioni <<a ymailto="mailto:matteo@umn.edu" href="/mc/compose?to=matteo@umn.edu">matteo@umn.edu</a>><br>> Subject: Re: [Pw_forum] U for Oxygen<br>> To: "PWSCF Forum" <<a ymailto="mailto:pw_forum@pwscf.org" href="/mc/compose?to=pw_forum@pwscf.org">pw_forum@pwscf.org</a>><br>> Date: Tuesday, August 4, 2009, 6:59 AM<br>><br>><br>><br>> Dear Ali,<br>><br>><br>><br>> ali kazempour wrote:<br>> > Dear Matteo<br>>
> I used your comment and followed your example for NiO and I<br>> succeed <br>> > to get U for TiO2. But in file Ur16.out I see three column .<br>> ><br>><br>> I don't have any three column section in any of my files. so if<br>> you want<br>> me to help you you have to report at least a section of your output<br>> file. This is a good habit actually in consideration of the fact that<br>> this is not a private conversation (I would have asked you in any<br>> case<br>> as I don't remember by heart the format of any file) between me<br>> and you<br>> but a message to the forum and you want
other people to understand<br>> what you are saying.<br>><br>> > The first is number of atom in supercell , second is U value for Ni<br>> > atom and I don,t know the third? does the third belong to U value<br>> > for Oxygen or not? Because the third column kas big value?<br>> ><br>> ><br>> > another question is for isolated atom Hubbard parameter. What do<br>> you<br>> > expect about the value of U for Isolated atom? Is this big value<br>> > (greater than 10 eV) or it would be tiny value?<br>> ><br>><br>> I think it will be meaningless for the reasons I explained in my
last<br>> email. To obtain a meaningful number for the isolated atom you<br>> probably<br>> have to abandon the idea to use a perturbation in the potential and<br>> change instead the number of electrons directly. This means you will<br>> have to do calculations on atoms having fractional charges which<br>> requires additional corrections if you use a code designed for<br>> periodic<br>> systems (crystals). However I have never done this isolated atom<br>> calculation of U before so I don't have more details about it.<br>> I see (from a private email) you are thinking of computing U for the<br>> isolated atom and to obtain a value for the crystal just
by<br>> dividing by<br>> the epsilon_inft. the method is proposed in<br>><br>> <a href="http://link.aps.org/doi/10.1103/PhysRevB.74.045202" target="_blank">http://link.aps.org/doi/10.1103/PhysRevB.74.045202</a><br>><br>> (which I haven't re-read yet).<br>><br>> I see a couple of problems:<br>><br>> 1) (not important for ZnO). suppose you have Fe3O4 with Fe2+ and<br>> Fe3+.<br>> these Fe ions likely have different U. how do you obtain<br>> a different number from the atomic code? would you do the calculation<br>> for isolated Fe2+ and Fe3+?<br>><br>> 2) how do you get epsilon? since it's a linear response property I<br>>
don't<br>> think its calculation is any cheaper than the direct calculation of U.<br>><br>> regards,<br>><br>> Matteo<br>><br>> > should we choose for running the script for isolated atom only<br>> gamma<br>> > point or we have to choose a fine mesh?<br>> > thanks a lot<br>> ><br>> ><br>> > Ali Kazempour<br>> > Physics department, Isfahan University of Technology<br>> > 84156 Isfahan, Iran. Tel-1: +98 311 391 3733<br>> > Fax: +98 311 391 2376 Tel-2: +98 311 391 2375<br>> ><br>> > --- On *Sun,
8/2/09, Matteo Cococcioni /<<a ymailto="mailto:matteo@umn.edu" href="/mc/compose?to=matteo@umn.edu">matteo@umn.edu</a><br>> </mc/compose?to=<a ymailto="mailto:matteo@umn.edu" href="/mc/compose?to=matteo@umn.edu">matteo@umn.edu</a>>>/* wrote:<br>> ><br>> ><br>> > From: Matteo Cococcioni <<a ymailto="mailto:matteo@umn.edu" href="/mc/compose?to=matteo@umn.edu">matteo@umn.edu</a><br>> </mc/compose?to=<a ymailto="mailto:matteo@umn.edu" href="/mc/compose?to=matteo@umn.edu">matteo@umn.edu</a>>><br>> > Subject: Re: [Pw_forum] occupation<br>> > To: "PWSCF Forum" <<a ymailto="mailto:pw_forum@pwscf.org"
href="/mc/compose?to=pw_forum@pwscf.org">pw_forum@pwscf.org</a><br>> </mc/compose?to=<a ymailto="mailto:pw_forum@pwscf.org" href="/mc/compose?to=pw_forum@pwscf.org">pw_forum@pwscf.org</a>>><br>> > Date: Sunday, August 2, 2009, 8:31 AM<br>> ><br>> ><br>> > Dear Ali,<br>> ><br>> > 1, -1, 0 are just spin indexes to tell the code what is the<br>> relative<br>> > magnetization of the atoms (parallel, antiparallel, or none). if<br>> > your system is non magnetic put all 0. or set magn = .false.<br>> and
put<br>> > nothing.<br>> > you should look at the examples on Fe and Si as well and<br>> learn from<br>> > there by comparison.<br>> ><br>> > Matteo<br>> ><br>> ><br>> ><br>><br>><br>> -- <br>> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br>> Matteo Cococcioni<br>> Department of Chemical Engineering and Materials Science,<br>> University of Minnesota<br>> 421 Washington Av. SE<br>>
Minneapolis, MN 55455<br>> Tel. +1 612 624 9056 Fax +1 612 626 7246<br>> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br>><br>> _______________________________________________<br>> Pw_forum mailing list<br>> <a ymailto="mailto:Pw_forum@pwscf.org" href="/mc/compose?to=Pw_forum@pwscf.org">Pw_forum@pwscf.org</a> </mc/compose?to=<a ymailto="mailto:Pw_forum@pwscf.org" href="/mc/compose?to=Pw_forum@pwscf.org">Pw_forum@pwscf.org</a>><br>> <a href="http://www.democritos.it/mailman/listinfo/pw_forum" target="_blank">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>><br>><br>> ------------------------------------------------------------------------<br>><br>> _______________________________________________<br>> Pw_forum
mailing list<br>> <a ymailto="mailto:Pw_forum@pwscf.org" href="/mc/compose?to=Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>> <a href="http://www.democritos.it/mailman/listinfo/pw_forum" target="_blank">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>> <br><br><br>-- <br>%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br>Matteo Cococcioni<br>Department of Chemical Engineering and Materials Science,<br>University of Minnesota<br>421 Washington Av. SE<br>Minneapolis, MN 55455<br>Tel. +1 612 624 9056 Fax +1 612 626 7246<br>%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br><br>_______________________________________________<br>Pw_forum mailing list<br><a ymailto="mailto:Pw_forum@pwscf.org" href="/mc/compose?to=Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br><a href="http://www.democritos.it/mailman/listinfo/pw_forum"
target="_blank">http://www.democritos.it/mailman/listinfo/pw_forum</a><br></div></blockquote></td></tr></table><br>