Yes, U depends on the type of atom, but of course also on the specific compound. For metallic Fe the U should be in the range of 0-2 eV at most, for some insulating compound with very localized states, it may go up to even 4-6 (maybe even 8) eV.
Am 26.06.2012 06:42, schrieb shamik chakrabarti: > Dear wien2k users, > > We generally choose the value of U by fitting it with > experimental band gap or by calculating it through linear response > method. Now my question is that whether U is element specific or depends > on the composite in which the element reside? (*if I consider same > magnetic configuration for all the composites I am referring here...as > antiferromagntism do produce a band gap even without applying any U*) > > To make it more clear, say for Fe d, I have seen in literature, people > have used U=4.5 to 5 eV......in some of our calculation we have even > used U=6 eV for Fe d to obtain better electronic structure having closer > match with experimental observation. Hence it looks that U for Fe d > orbital can have value ranging from 4.5-6 eV...& that mean U is not > element specific rather it depends on the composite in which the element > exist (I again want to insist that if I consider same magnetic > configuration for all the composites). Am I right? > > with regards, > > -- > Shamik Chakrabarti > Senior Research Fellow > Dept. of Physics & Meteorology > Material Processing & Solid State Ionics Lab > IIT Kharagpur > Kharagpur 721302 > INDIA > > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > -- Peter Blaha Inst.Materials Chemistry TU Vienna Getreidemarkt 9 A-1060 Vienna Austria +43-1-5880115671