dear Ali, I will try to answer your questions
ali kazempour wrote: > Dear All > I have some questions about LDA+U nature. Does U treate like a > perturbation( I know that GW( many body peturbation method) is > modified version of LDA+U? if yes why we are allowed to take > U=0,1,2,........ up to large values? and why we solve system > self-consistent? > no, U is not treated as a perturbation. it is more a correction to the "standard" DFT energy functional. you can check the relationship between +U and GW in the following reference (probably there are many more): Anisimov et al, Journal of Physics: Condensed Matter 9, 767 (1997) > Does U comute with KS-hamiltonian in every U values? I mean does the > order of states remains intact with respect to LDA or they can change? > and final question: > For sure the +U correction to the potential commutes with the translation and other symmetries of the crystal. I think it doesn't commute with the rest of the Hamiltonian (the unperturbed DFT one). So if you think to switch on the U from a U=0 ground state, unless the KS states are already bloch sums of atomic orbitals (that would be a very unlikely accident) the +U correction introduces interactions between them if allowed by symmetry and you are going to get a non trivial mixing of them besides a shift in the eigenvalue. Probably the most significant modifications are going to take place for states around the Fermi level that may get more localized. The ones that are deeper in energy are probably closer to be atomic-like already and they will, at most, get a shift in the corresponding eigenvalues. > What is the effect of U on > 1-empty states in conduction band (with d-character) > pushed up > 2-half filled states in conduction band(with d-character) > depends: see above > 3-filled- states in conduction band (with d-character) > pushed down > Thanks a lot > > > Ali Kazempour > > hope this helps. Matteo > > Fritz-Haber-Institut fax : ++49-30-8413 4701 > der Max-Planck-Gesellschaft > Faradayweg 4-6 e-mail: kazempou at fhi-berlin.mpg.de > D-14 195 Berlin-Dahlem / German > > > ------------------------------------------------------------------------ > > _______________________________________________ > 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 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
