Dear developers, I have observed a mismatch between k-points generated by means of kpoints.x and phonons program, ph.x.
The problem is that first I did phonon calculations for a base centered orthorhombic cell (ibrav=9) using 4x2x2 mesh (10 q-points) and got an error message from q2r.x "q not allowed". Well, something is wrong with the q-points. Then I tried to generate q-points using kpoints.x which stated that 4x2x2 mesh "has not the correct symmetry" and gave only 6 q-points. OK, I used 4x3x3 to generate q-points and got 10 q-points without any message from kpoints.x. But when I started phonons with 4x3x3 q-mesh, the ph.x program generated 14 q-points. Can someone explain such kind discrepancy between two programs generating q-points? I used c/a=1.720447 and b/a=1.857204. Bests, Eyvaz. ------------------------------------------------------------------- Prof. Eyvaz Isaev, Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden Condensed Matter Theory Group, Uppsala University, Sweden Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com --- On Sun, 10/5/08, willy kohn <willykohn at gmail.com> wrote: > From: willy kohn <willykohn at gmail.com> > Subject: Re: [Pw_forum] Quick question on Hartwigsen-Goedeker-Hutter > pseudopotential > To: eyvaz_isaev at yahoo.com, "PWSCF Forum" <pw_forum at pwscf.org> > Date: Sunday, October 5, 2008, 5:33 AM > Dear Eyvaz: > Thank you for your long reply. What you mentioned was > correct. I didn't > expect LDA PP's can gave me a good prediction to the > band gap and in fact > the band gap given by the PP is closer to the experimental > data than other > PP's. What I would like to know is what value for Ge is > 'typical' or > 'normal' for a LDA PP. > > Best, > > Wei > > On Thu, Oct 2, 2008 at 7:10 PM, Eyvaz Isaev > <eyvaz_isaev at yahoo.com> wrote: > > > Dear Willy, > > > > --- On Fri, 10/3/08, willy kohn > <willykohn at gmail.com> wrote: > > > > > I was told that with a LDA PP, Ge has a vanishing > > > or negative band gap at Gamma point. But with > this PP, > it has a gap of > > 0.50eV (using experimental lattice) or > > > 0.80 eV (after relaxation). > > > > Please recall that we use the Density Functional > Theory, that is the theory > > of the ground state, and it is not obliged to give > correct excitation > > energies in semiconductors. Besides, we apply the > Local Density > > Approximation which underestimates the band gap, even > gives negative band > > gap in Ge. This is well known fact. The source of this > fault is the use of > > single-particle Shrodinger equation, but the use of > the quasiparticle > > equation with the self-energy operator is more > correct. There are few > > recipes how to deal with this equation. The so called > GW method is among > > them. > > > > Another point is proper account of > exchange-correlation interactions. It is > > well known that the use of the functionals like PBE0, > B3LYP gives improved > > results for insulating systems concerning their > electronic structure. For > > the reference please have a look at /examples-EXX (for > Si). > > > > So, if the HGH pseudopotentials are used in the > framework of the DFT-LDA, > > unlikely they can give correct band gap due to the > fault of the underlying > > method. > > Even all-electron methods within the LDA fail to > predict the band gap (as > > example see PHYSICAL REVIEW B 67, 155208 2003). > > > > Bests, > > Eyvaz. > > > > > ------------------------------------------------------------------- > > Prof. Eyvaz Isaev, > > Theoretical Physics Department, Moscow State Institute > of Steel & Alloys, > > Russia, > > Department of Physics, Chemistry, and Biology (IFM), > Linkoping University, > > Sweden > > Condensed Matter Theory Group, Uppsala University, > Sweden > > Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, > eyvaz_isaev at yahoo.com > > > > > > > > > > > > > > > I'm not sure what I > > > knew is correct, and that is the reason I wanted > another PP > > > to verify. > > > > > > Best, > > > > > > Wei > > > > > > > > > > > > On Thu, Oct 2, 2008 at 2:12 PM, Axel Kohlmeyer > > > <akohlmey at cmm.chem.upenn.edu>wrote: > > > > > > > On Thu, 2 Oct 2008, willy kohn wrote: > > > > > > > > WK> Hi, Axel: > > > > WK> > > > > WK> Thanks a lot for your quick answer. I > need to > > > do some calculations on > > > > some > > > > WK> compound semiconductors of Ge. But > the PP > > > (Ge.pz-bhs.UPF) provided in > > > > the > > > > WK> PWSCF website yeided some results > that I > > > don't understand. So I would > > > > like > > > > > > > > perhaps it would be useful to explain in > more detail > > > what > > > > is confusing you and what calculation you > did with > > > what input. > > > > perhaps some people here can comment on it. > it is > > > always easy > > > > to blame the pseudopotential (sometimes > rightfully > > > so), but > > > > more often than not, the real cause is in > not doing a > > > calculation > > > > correctly, or not using a pseudopotential > correct. > > > > > > > > WK> to use some other PP's to check > if I did > > > the calculation correctly. Any > > > > WK> suggestions? > > > > > > > > i have a set of Ge pseudopotentials > generated from > > > parameters > > > > for a norm-conserving troullier-martins > potential that > > > is in > > > > the extended CPMD psp library. they have > seen only > > > very minimal > > > > transferability testing (using an atomic > code in > > > bessel basis), > > > > but so far seem to be ok, except for the > OLYP one > > > which has a > > > > ghost in the s-channel. > > > > > > > > i can send them to you in a private mail, if > you are > > > interested. > > > > no guarantees etc... > > > > > > > > cheers, > > > > axel. > > > > > > > > WK> > > > > WK> Best, > > > > WK> > > > > WK> Wei > > > > WK> > > > > WK> On Thu, Oct 2, 2008 at 11:54 AM, Axel > Kohlmeyer > > > < > > > > akohlmey at cmm.chem.upenn.edu > > > > WK> > wrote: > > > > WK> > > > > WK> > On Thu, 2 Oct 2008, willy kohn > wrote: > > > > WK> > > > > > WK> > WK> Dear PWSCF users: > > > > WK> > WK> > > > > WK> > WK> I have a quick question > about using > > > > WK> > WK> > Hartwigsen-Goedeker-Hutter< > > > > WK> > > > > > > > > > > > http://cvs.berlios.de/cgi-bin/viewcvs.cgi/cp2k/potentials/Goedecker/abinit/pade > > > > WK> > >pseudopotential > > > > WK> > WK> with PWSCF. Is there any > converter > > > to transfer the HGH pp > > > > WK> > WK> format to UPF used in > PWSCF? > > > > WK> > > > > > WK> > none that i am aware of. > > > > WK> > > > > > WK> > the GTH pseudopotentials are > analytical in > > > real and reciprocal > > > > WK> > space and to incorporate them > properly, > > > one would have to do a > > > > WK> > lot of programming. in the CPMD > code (from > > > http://www.cpmd.org) > > > > WK> > they are treated as a special > case, > > > similar to ultra-soft psps. > > > > WK> > > > > > WK> > is there any particularly reason > you'd > > > need any of those? > > > > WK> > > > > > WK> > cheers, > > > > WK> > axel. > > > > WK> > > > > > WK> > > > > > WK> > WK> > > > > WK> > WK> Best, > > > > WK> > WK> > > > > WK> > WK> Wei > > > > WK> > WK> > > > > WK> > WK> Georgia Tech > > > > WK> > WK> > > > > WK> > > > > > WK> > -- > > > > WK> > > > > > > > > > ======================================================================= > > > > WK> > Axel Kohlmeyer > > > akohlmey at cmm.chem.upenn.edu > > > > http://www.cmm.upenn.edu > > > > WK> > Center for Molecular Modeling > -- > > > University of Pennsylvania > > > > WK> > Department of Chemistry, 231 > S.34th > > > Street, Philadelphia, PA > > > > 19104-6323 > > > > WK> > tel: 1-215-898-1582, fax: > 1-215-573-6233, > > > office-tel: > > > > 1-215-898-5425 > > > > WK> > > > > > > > > > ======================================================================= > > > > WK> > If you make something > idiot-proof, the > > > universe creates a better > > > > idiot. > > > > WK> > > > > > WK> > > > > > > > > -- > > > > > > > > ======================================================================= > > > > Axel Kohlmeyer akohlmey at cmm.chem.upenn.edu > > > http://www.cmm.upenn.edu > > > > Center for Molecular Modeling -- > University of > > > Pennsylvania > > > > Department of Chemistry, 231 S.34th Street, > > > Philadelphia, PA 19104-6323 > > > > tel: 1-215-898-1582, fax: 1-215-573-6233, > > > office-tel: 1-215-898-5425 > > > > > > > > ======================================================================= > > > > If you make something idiot-proof, the > universe > > > creates a better idiot. > > > > > > > _______________________________________________ > > > 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
