Hi Lorenzo, the two tutorial should be quite equivalent, although the one Federico found is more recent and probably I updated some details.
Regarding your questions: as far as I understand you are only interested in U on one specific atomic species of your materials. You could do that by doing two perturbations: one on the atom you are interested in, the second on all the other atoms (which you treat as a "macro-atom") at the same time. Of course the occupation of this second "extended atom" is the sum of the occupations of the atoms it is composed by. you then construct a 2x2 response matrix that, once inverted, should give you the U you are looking for (throwing away the one for the "macro-atom"). This only limits the number of perturbation but still requires a supercell of sufficiently large size. We are working on a way to make the whole procedure more efficient, through automatizing the linear-response, but the code is not ready yet. Best, Matteo On Fri, Sep 2, 2016 at 5:55 PM, Lorenzo Paulatto < [email protected]> wrote: > Hello, > I have a question about how to compute the abinitio U, I'm following the > online Santa Barbara 2009 tutorial (and trying to use the script therein) > and > PRB 71, 35105 (2005). > > I have a system that is not very large but quite heavy to compute, and have > several atomic species (3 at first, then 4) but only one is problematic, > as it > is could be Cerium or other Lanthanoids. > > It would be quite anoying and very cpu time consuming for me to properly* > compute U by finite response for all the species, but I'm not sure that > 1. it is possible with the available toolchain > 2. it makes sense > > Also, if somebody (e.g. Matteo) has some more recent and/or more user > friendly > code to compute dalpha/dn I'm a taker. > > thank you for your help! > > *) by properly I mean take care that it is converged with the supercell > size > > -- > Dr. Lorenzo Paulatto > IdR @ IMPMC -- CNRS & Université Paris 6 > +33 (0)1 44 275 084 / skype: paulatz > http://www.impmc.upmc.fr/~paulatto/ > 23-24/4é16 Boîte courrier 115, > 4 place Jussieu 75252 Paris Cédex 05 > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum >
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