On 07/30/2011 04:55 AM, Masoud Nahali wrote: > > Dear Hongsheng > > In this case I think that the more important issue to be noticed is > considering spin polarization for most of atoms. Many mistakes in this > issue arise from not considering spin polarization. > I guess Considering "Symmetry" may symmetrize the charge density and > causes some changes in electronic structure of atom (population of > orbitals) or may do reversely with nosym='true'. > Also, it is impossible for me to describe this issue based on DFT and > the exchange-correlation parts in details. > > In quantum chemistry software based on Gaussian type orbitals basis set > (not plane wave basis set)
When using plane wave basis set, say, pwcsf/vasp/castep and so on, what will happen in that case? > we compare energy of an atom with considering > different spin multiplicities then find the lowest energy and call it > "ground state". In plane-wave-basis-set based codes, we also can find the "ground state", what's the differences between these two "ground state" obtained by different basis sets? > I can do it for some atoms (whatever you select) by > Firefly software (former PC-GAMESS) and then you can compare it with the > corresponding calculation by QE. I want to know: does this comparison make sense? > These days I am very busy and going on a journey so let me do it in a > due course; contact me :) Thanks a lot for your kindly help and reply ;-) > > Best Wishes > > Masoud > > > > -------------- > Masoud Nahali, Sharif University of Technology > masoud.nahali at gmail.com <mailto:masoud.nahali at gmail.com>; a > <http://alum.sharif.edu/%7Em_nahali>lum.sharif.edu/~m_nahali > <http://lum.sharif.edu/~m_nahali> > > PSave a Tree . . . Please don't print this e-mail unless you really need to. > > > > Hongsheng Zhao Wrote : > > Thanks a lot for all of the helps on this topic. I've checked and > read > most the topics on this ML which are related to "calculating the energy > of isolated atom". It seems this is a tricky thing based on most of > the replies on this similar topics on this ML. > > Based on my understanding, till now, there are still some issues > puzzling me on this topic: > > 1- On the manual of pwscf (p37), we can find the following descriptions: > > -------- > ... > Specify nosym=.true. to avoid generation of additional k-points in low > symmetry > ... > ----------- > > I want to know, by using nosym=.true., what's the different on the > k-points set obtained with the ones without using this option? For > example, when using a bcc box with a atom at its center, what's the > corresponding k-points set when using nosym=.true.? > > Furthermore, when we say a isolated atom, we mean a zero dimension > system. So the corresponding BZ sampling by using gamma only should be > OK. If so, there is no k-points issues at all - there only one k point > should be considered. Hence I'm confused on the description given by > the manual *avoid generation of additional k-points in low symmetry*. > Any hints? > > 2- From this ML, I found the following notes: > > --------- > while doing calculations for any zero dimensions you should always set > nosym =.true. > ----------- > > Does this mean: when I do the calculations for isolated > atom/molecule/nanocluster and so on, I should always set nosym =.true.? > > 3- Prof. Paolo Giannozzi given the following descriptions on some > similar topic in this ML: > > --------- > calculations on isolated atoms with plane waves are tricky. > Compare your results with what you get with the atomic code, > in which you can fix occupancies at will > ------------ > > My issue: how to fix the occupancies based on the results? Any > examples? > > What do you mean by saying *at will*? If really is a thing *at will*, > why should we do it? > > Regards > > > > > On Thu, Jul 28, 2011 at 10:12 AM, Gabriele Sclauzero > > <gabriele.sclauzero at epfl.ch <mailto:gabriele.sclauzero at epfl.ch> > <mailto:gabriele.sclauzero at epfl.ch > <mailto:gabriele.sclauzero at epfl.ch>>> wrote: > > > > > > Il giorno 28/lug/2011, alle ore 01.55, Hongsheng Zhao ha scritto: > > > >> Hi all, > >> > >> I've learned that when using the a large-cell ( i.e., a big > box ) to > >> calculate the energy of isolated atom, it should be done without > >> symmetry. But I'm not sure what's the meaning of the "without > >> symmetry" here and how to ensure this when we using a a big box > >> model > >> for this purpose. Any hints on this issue? > > > > This is a FAQ on this forum: have you spent some time > browsing the > > archives? > > > > OK, I'll give you a hint: "nosym"... but use it with care! > > > > HTH > > > > GS > > > >> > >> Regards > >> -- > >> Hongsheng Zhao <zhaohscas at yahoo.com.cn > <mailto:zhaohscas at yahoo.com.cn> > >> <mailto:zhaohscas at yahoo.com.cn <mailto:zhaohscas at yahoo.com.cn>>> > >> School of Physics and Electrical Information Science, > >> Ningxia University, Yinchuan 750021, China > >> _______________________________________________ > >> Pw_forum mailing list > >> Pw_forum at pwscf.org <mailto:Pw_forum at pwscf.org> > <mailto:Pw_forum at pwscf.org <mailto:Pw_forum at pwscf.org>> > >> http://www.democritos.it/mailman/listinfo/pw_forum > > > > > > ? Gabriele Sclauzero, EPFL SB ITP CSEA > > / PH H2 462, Station 3, CH-1015 Lausanne/ > > > > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum -- Hongsheng Zhao <zhaohscas at yahoo.com.cn> School of Physics and Electrical Information Science, Ningxia University, Yinchuan 750021, China
