Dear Ali, your email is confusing so I don't know if I will be able to answer.
calculations of U on isolated atoms are problematic (why do you want to do that?) because the system has a discrete set of energy levels and so linear response based on the continuum variation of on-site occupations have little meaning. Also there is no way the electrons can move on other energy levels when you perturb entire l multiplets unless the pertubation is of the same order of the energy difference. yes if you compute the U in the bulk (a supercell is a bulk calculation) you obtain a different value. you actually need to study the convergence of U with the size of the supercell used in its calculation. hope this helps. regards, Matteo ali kazempour wrote: > Dear all > My results after doing LDA+U is very strange for isolated Ti atoms. > For d(alpha)/d(n) I see discontinuities .is our result true? And is > any way to correct that? > Another question:If our calculation for U instead in the bulk, would > be done in big supercell, Do I get different value for U or both are same? > 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 > > > ------------------------------------------------------------------------ > > _______________________________________________ > 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 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
