Thanks Dr. Matteo. That is helpful. On Tue, Jul 10, 2012 at 11:15 AM, Matteo Cococcioni <matteo at umn.edu> wrote:
> Dear Peng, > > let me add one word to Burak's. > you need to distinguish two O kinds anyway, whether you shift the > atomic position or not. if you don't do that you will be perturbing > all the oxygen atoms at the same time. > The necessity to have the perturbed atom described as of a different > type (although with the same pseudopotential) is what makes it > convenient (most of the time) to place it at the origin of the unit > cell. > > best, > > Matteo > > > > On Tue, Jul 10, 2012 at 10:03 AM, Peng Chen <pchen at ion.chem.utk.edu> > wrote: > > When O is perturbed in the case of NiO in tutorial, it > is re-positioned and > > there are 2 different kinds of O (first with 1 atom, the second with 7 > > atoms). Then the kind with only one O is perturbed. In the tutorial, it > > reads "This is done to preserve the largest possible number of > symmetries". > > Is this process necessary? Can we just run computation without > re-position? > > In that case, there is only one kind of O with 8 atoms. > > > > In the position file "filepos", the scale of cell length is always 10, > even > > if the scale is 7.9 in NiO and 5.42 in Fe. Shall we always use 10 in > > position file no matter what the real scale is? > > > > On Tue, Jul 10, 2012 at 9:37 AM, Burak Himmetoglu <himm0013 at umn.edu> > wrote: > >> > >> Hi Peng, > >> > >> r.x assigns the values of the response matrices only by considering the > >> distance between atoms and whether they have the same spin and type or > not. > >> This information has to be given by the user in the positions file > "filepos" > >> read by &input_mat. If B(1) and B(2) are different types > >> (e.g. crystallographically) you should perturb them separately, as you > >> outlined in the procedure, and make sure that ntyp=3 (type 1 is B(1), > type 2 > >> is B(2) and type 3 is O) in the namelist &input_mat that goes into r.x > >> > >> Best regards, > >> > >> Burak > >> > >> > >> On Tue, Jul 10, 2012 at 1:45 AM, Stefano de Gironcoli < > degironc at sissa.it> > >> wrote: > >>> > >>> I don't know the details of r.x code but I think that, physically, what > >>> matters is the two atoms are crystallographically equivalent or not > >>> .therefore I think space group symmetry is the relevant one. > >>> > >>> stefano > >>> > >>> > >>> On 07/10/2012 05:54 AM, Peng Chen wrote: > >>> > >>> Dear All, > >>> > >>> In the calculation of U, how can we determine the equivalence of the > >>> ions, > >>> by site symmetry or space group symmetry? > >>> E.g ABO3, B ions has 2 different site symmetries (B(1) B(2)). Shall we > >>> run > >>> calculation on perturbing B(1) and B(2) ions or just a B ion? > >>> > >>> In order to find U in B ions, I tried to run calculation with > >>> perturbing > >>> just on B, and r.x gave some errors that it needs to read more data. > >>> So I guess it needs the perturbed data from other atoms. Shall I use > the > >>> procedures listed below? > >>> 1. run scf calculation with Hubbard_U(i)= 1.d-20 > >>> 2. run scf with perturbing on an A ion > >>> 3. run scf with perturbing on a B(1) ion > >>> 4. run scf with perturbing on a B(2) ion > >>> 5. run scf with perturbing on an O ion > >>> > >>> > >>> > >>> > >>> > >>> > >>> _______________________________________________ > >>> Pw_forum mailing list > >>> Pw_forum at pwscf.org > >>> http://www.democritos.it/mailman/listinfo/pw_forum > >>> > >>> > >>> > >>> > >>> _______________________________________________ > >>> Pw_forum mailing list > >>> Pw_forum at pwscf.org > >>> http://www.democritos.it/mailman/listinfo/pw_forum > >>> > >> > >> > >> _______________________________________________ > >> Pw_forum mailing list > >> Pw_forum at pwscf.org > >> http://www.democritos.it/mailman/listinfo/pw_forum > >> > > > > > > > > -- > > Best Regards. > > Peng > > > > _______________________________________________ > > 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 > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- Best Regards. Peng -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120710/5c652eff/attachment-0001.htm
