<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"><DIV>Dear Matteo</DIV>
<DIV>Thanks many for your reply. But my special case is for the defect states (has d-character )in TiO2 that is in resonance with conduction band and is filled with 2 electrons. When I increased the U from 1 to 4 I saw that the defect state bieng pushed up instead lowering of this state as we expected from theory of LDA+U. Is it true? Moreover for another defect state that is empty and is above conduction band I saw it being peshed down in contrast with LDA+U expection. But when I perform GW@ GGA+U I see that the behavior is reversed in which empty states being pushed up while filled state is pushing down. what does it mean? is it rational?</DIV>
<DIV>thanks a lot<BR><BR>Ali Kazempour<BR><BR><BR><BR>Fritz-Haber-Institut fax : ++49-30-8413 4701<BR>der Max-Planck-Gesellschaft<BR>Faradayweg 4-6 e-mail: kazempou@fhi-berlin.mpg.de<BR>D-14 195 Berlin-Dahlem / German<BR><BR>--- On <B>Sun, 7/4/10, Matteo Cococcioni <I><matteo@umn.edu></I></B> wrote:<BR></DIV>
<BLOCKQUOTE style="BORDER-LEFT: rgb(16,16,255) 2px solid; PADDING-LEFT: 5px; MARGIN-LEFT: 5px"><BR>From: Matteo Cococcioni <matteo@umn.edu><BR>Subject: Re: [Pw_forum] LDA+U character<BR>To: "PWSCF Forum" <pw_forum@pwscf.org><BR>Date: Sunday, July 4, 2010, 8:29 PM<BR><BR>
<DIV class=plainMail><BR>dear Ali,<BR><BR>I will try to answer your questions<BR><BR><BR><BR>ali kazempour wrote:<BR>> Dear All<BR>> I have some questions about LDA+U nature. Does U treate like a <BR>> perturbation( I know that GW( many body peturbation method) is <BR>> modified version of LDA+U? if yes why we are allowed to take <BR>> U=0,1,2,........ up to large values? and why we solve system <BR>> self-consistent?<BR>><BR><BR>no, U is not treated as a perturbation. it is more a correction to the <BR>"standard" DFT energy functional. you can check the relationship between <BR>+U and GW in the following<BR>reference (probably there are many more):<BR><BR>Anisimov et al, Journal of Physics: Condensed Matter 9, 767 (1997)<BR><BR><BR>> Does U comute with KS-hamiltonian in every U values? I mean does the <BR>> order of states remains intact with respect to LDA or they can change?<BR>> and final
question:<BR>><BR><BR>For sure the +U correction to the potential commutes with the <BR>translation and other symmetries of the crystal.<BR>I think it doesn't commute with the rest of the Hamiltonian (the <BR>unperturbed DFT one). So if you think to switch on the U from a<BR>U=0 ground state, unless the KS states are already bloch sums of atomic <BR>orbitals (that would be a very unlikely accident) the +U correction<BR>introduces interactions between them if allowed by symmetry and you are <BR>going to get a non trivial mixing of them besides a shift in the<BR>eigenvalue. Probably the most significant modifications are going to <BR>take place for states around the Fermi level that may get more localized.<BR>The ones that are deeper in energy are probably closer to be atomic-like <BR>already and they will, at most, get a shift in the corresponding <BR>eigenvalues.<BR><BR>> What is the effect of U on<BR>> 1-empty states in conduction band
(with d-character)<BR>><BR><BR>pushed up<BR><BR>> 2-half filled states in conduction band(with d-character)<BR>><BR><BR>depends: see above<BR><BR>> 3-filled- states in conduction band (with d-character)<BR>><BR><BR>pushed down<BR><BR>> Thanks a lot<BR>><BR>><BR>> Ali Kazempour<BR>><BR>><BR><BR><BR>hope this helps.<BR><BR>Matteo<BR><BR><BR>><BR>> Fritz-Haber-Institut fax : ++49-30-8413 4701<BR>> der Max-Planck-Gesellschaft<BR>> Faradayweg 4-6 e-mail: <A href="http://us.mc1144.mail.yahoo.com/mc/compose?to=kazempou@fhi-berlin.mpg.de" ymailto="mailto:kazempou@fhi-berlin.mpg.de">kazempou@fhi-berlin.mpg.de</A><BR>> D-14 195 Berlin-Dahlem / German<BR>><BR>><BR>> ------------------------------------------------------------------------<BR>><BR>> _______________________________________________<BR>> Pw_forum mailing list<BR>> <A
href="http://us.mc1144.mail.yahoo.com/mc/compose?to=Pw_forum@pwscf.org" ymailto="mailto: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 href="http://us.mc1144.mail.yahoo.com/mc/compose?to=Pw_forum@pwscf.org" ymailto="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</A><BR><A href="http://www.democritos.it/mailman/listinfo/pw_forum"
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