Hi Andrei, Thanks a lot for the explainations and the example for Cr.
SIESTA manuel mentioned that to generate a polarization orbital one needs to use "P" in PAO.Basis. However, I saw from Siesta website that in some of the optimized basis sets, for example Ti and Mn, only a normal single zeta (4p) is used as a polarization orbital. It is mentioned in the notes for these bases that this normal single zeta is intended for polarization. Of course, this is not the definition of a polarization orbital in the SIESTA manuel. I don't know the reason why people use a normal single zeta rather than following the manuel. Is it better in some cases? Or, it is not a justified method? By the way, do you have a tested basis sets for Cr, V? I have pseudopotential for Cr and V without semicore states. The magnetic moments are too high, so semicore states are necessary. I'm currently testing PP's for Cr and V from a publication with DZP, which will be generated by the method I learned today. I'll be very grateful if you can send me PP's and basis, if you have some. Thanks again. Best wishes, Xiaobing Quoting Andrei Postnikov <[EMAIL PROTECTED]>: > Hallo Marcos and Xiaobing - > in a recent exchange of opinions about basis sets > (and polarization orbitals) I'm afraid that something wrong > has been pronounced, even if I know very few about basis sets. > First, polarization orbitals are NOT just orbitals > with orbital moment l+1; they are orbitals constructed > in a very special way. In this sense, > | > > | > n= 3 0 2 > | > 0.000 0.000 > | > 1.000 1.000 > | > n= 3 1 1 # <-- Single polarization for the 3s orbital above > | > 0.000 # double polarization would be two zetas > > the latter entry IS NOT "single polarization for the 3s orbital" > but, rather, a genuine atomic 3p orbital. Even as they have the same > l-dependence, polarization orbitals have very different radial shape > from geniune atomic orbitals. They are added in order to expand > the flexibility of (in this case) 3s orbitals, rather than incorporate > genuine 3p orbitals, which might lie quite high, and be irrelevant > (say, if we discuss an element with an empty 3p shell). > Speaking about the confinement of polarization orbitals, it is > exactly the same as of their parent orbitals. > These issues are thoroughly covered in "basic" Siesta papers > about basis construction, tutorials etc. > > But I think Xiaobing's initial question was about 3p as semicore states > in transition metals, and in this relation the answer about > polarization orbitals goes beyond the point; semicore states are > quite localized and are not so much subject to perturbations which would > demand the inclusion of THEIR polarization orbitals. > (But of course it is perfectly legal to do this. The result > for semicore 3p won't be 3d orbitals, however). > In order to include the semicore 3p > it would normally suffice merely to include them > explicitly in the basis, like e.g. in my naive input for Cr: > %block PAO.Basis > Cr 3 0.0 > n=4 0 2 P > 0.0 0.0 > n=3 2 3 > 0.0 0.0 0.0 > n=3 1 2 > 0.0 0.0 > %endblock PAO.Basis > > Best regards > > Andrei > > +-- Dr. Andrei Postnikov ---- Tel. +33-387315873 ----- mobile +33-666784053 > ---+ > | Paul Verlaine University - Institute de Physique Electronique et Chimie, > | > | Laboratoire de Physique des Milieux Denses, 1 Bd Arago, F-57078 Metz, > France | > +-- [EMAIL PROTECTED] ------ http://www.home.uni-osnabrueck.de/apostnik/ > --+ > > On Wed, 23 Jan 2008, X. Feng wrote: > > | Hi Marcos, > | > | Thanks very much for the reply, it is really very helpful to me. > | I noticed that a lot people are not using "P" in Pao.Basis to > | generate polarization orbital, rather they use, like in your example, > | a normal single zeta orbital. With "P" the radius cannot be freely > | changed, but it is polarized by using an electric field. > | So, this means that the radius of a polarization orbital is more > | important than polarization by electric field. Is it right? > | In terms of accuracy, do you think the method for polarization > | in your example is better than "P" method? (assuming that the basis sets > | for both methods are optimized) > | > | Thanks again, > | Yours > | > | Xiaobing > | > | Quoting Marcos Verissimo Alves <[EMAIL PROTECTED]>: > | > | > Hi Xiaobing, > | > > | > In principle, this should be it. Unless you have sometthing in mind for a > | > particular orbital or even a zeta, in which case you can set it with a > | > certain rc and let the others be determined by siesta. This is useful, > for > | > example, if you want to explicitly control the extension of your > | > polarisation orbitals: instead of having > | > > | > n= 3 0 2 P > | > 0.000 0.000 > | > 1.000 1.000 > | > > | > you include an orbital with a unit of angular momentum higher than the > one > | > it polarizes: > | > > | > n= 3 0 2 > | > 0.000 0.000 > | > 1.000 1.000 > | > n= 3 1 1 # <-- Single polarization for the 3s orbital above > | > 0.000 # double polarization would be two zetas > | > 1.000 > | > > | > > | > and set the rc explicitly. I'm not sure now, but I think that sometimes > | > siesta can complain about the rc's of polarization orbitals included in > | > this manner, telling you to set their rc explicitly. > | > > | > Cheers, > | > > | > Marcos > | > > | > > | > > | > Vous avez écrit / You have written / Lei ha scritto / Você escreveu... X. > | > Feng > | > > Dear everyone, > | > > > | > > Some people used DZP basis (not optimized) for some transition metals > with > | > > semicore states, like V, Cr. I don't know how they do it. > | > > Is it simply to set all cutoff radii to zeroes in the PAO.Basis and > | > > let SIESTA to generate these radii? One can only use hard confinement > | > > this way. > | > > Could somebody having such experience give me a clarification? > | > > Many thanks in advance. > | > > > | > > Yours, > | > > Xiaobing > | > > > | > > > | > > ---------------------------------------------------------------- > | > > This message was sent using IMP, the Internet Messaging Program. > | > > > | > > | > > | > -- > | > Dr. Marcos Verissimo Alves > | > Post-Doctoral Fellow > | > Unité de Physico-Chimie et de Physique des Matériaux (PCPM) > | > Université Catholique de Louvain > | > 1 Place Croix du Sud, B-1348 > | > Louvain-la-Neuve > | > Belgique > | > > | > ------ > | > > | > Gort, Klaatu barada nikto. Klaatu barada nikto. Klaatu barada nikto. > | > > | > | > | > | > | ---------------------------------------------------------------- > | This message was sent using IMP, the Internet Messaging Program. > | > | ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.
