Hi, In addition to Stefano's comment I would recommend check your input file by means of XCrysDen? in order to see whether you have correct structure. At this time it seems to be incorrect.
Besides, use lower convergence threshold, conv_thr=1d-8, 1e-6 looks quite high. 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 Wed, 7/9/08, Stefano Baroni <baroni at sissa.it> wrote: From: Stefano Baroni <[email protected]> Subject: Re: [Pw_forum] negative value of polarization and Z* for Pb in Tetragonal PbTiO3 and discrepancy To: "sathya subramanyan" <sathya_sheela1985001 at rediffmail.com>, "PWSCF Forum" <pw_forum at pwscf.org> Date: Wednesday, July 9, 2008, 3:53 AM what I was suggesting is that YOU perform a convergence test and ley us know ...SB On Jul 8, 2008, at 6:44 PM, sathya subramanyan wrote: ? Dear Sir, ? ? ? ? ? ? I have checked the k -point sampling for the tetragonal PbTiO3 and I hope that the k-point sampling is alright. I am giving below the input file for your reference. Pl, let me know if anything is wrong in the input.: ? THE I/P FILE FOR TETRAGONAL PbTiO3 &CONTROL ? ? calculation? = 'nscf' ? ? pseudo_dir? ? = '/home/nbaski/espresso-4.0/pseudo/' ? ? outdir? ? ? ? = '/home/nbaski/tmp/' ? ? lberry? ? ? ? = .true. ? ? gdir? ? ? ? ? = 3 ? ? nppstr? ? ? ? = 7 / &SYSTEM ? ? ibrav? ? ? ? = 6 ? ? ? celldm(1)? ? = 7.3415 ? ? celldm(3)? ? = 1.0653 ? ? nat? ? ? ? ? = 5 ? ? ntyp? ? ? ? ? = 3 ? ? nbnd? ? ? ? ? = 22 ? ? ecutwfc? ? ? = 30.0 ? ? occupations? = 'fixed' ? ? degauss? ? ? = 0.00 / &ELECTRONS ? conv_thr? ? ? = 1e-5 ? ? mixing_beta? = 0.3 / ATOMIC_SPECIES ? Pb? 207.2? ? ? Pb.vdb.UPF ? Ti? ? 47.867? ? Ti.vdb.UPF ? O? ? 15.9994? O.vdb.UPF ATOMIC_POSITIONS ? Pb? ? 0.00000? ? 0.00000? ? 0.01000 ? Ti? ? 0.50000? ? 0.50000? ? 0.53770 ? O? ? 0.50000? ? 0.50000? ? 0.11180 ? O? ? 0.00000? ? 0.50000? ? 0.61740 ? O? ? 0.50000? ? 0.00000? ? 0.61740 K_POINTS {automatic} ? 4 4 7? 1 1 1 Thank you in advance for any help SATHYA SHEELA.S Grad. Student Department of Physics National Institute of Technology Tiruchirapalli On Fri, 27 Jun 2008 Stefano Baroni wrote : >the sum of the all the effective charges should be zero for any? structure, >due dynamical charge neutrality (or acoustic sum rule, or? whatever you want >to call the fact that a homogeneouse electric field? will not exert a net >(and infinite!) force on a crystal. Vioation of? this charge >neutrality/acoustic sum rule are often due to numerical? inaccuracy, often >inaccurate k-point sampling. you may want to check? the convergence of your >calculations with respect to the number of k? points and/or try to calculate >the effective charges using linear- response theory. SB > >On Jun 27, 2008, at 11:51 AM, sathya subramanyan wrote: > >> >>Dear Developers, >>? ? ? ? ? ? ? ? I am trying to calculate the Berry Phaze? Polarization and >>effective charge on Pb(with the displacement of . 01*ao) for >>PbTiO3(tetragonal) but am getting a negative value, using? quantum espresso >>ver 4.0. >> >>? ? ? ? ? ? ? ? When I run the example 10 for cubic phase the? polarization >>and the Z* comes out to be alright. But, when I try for? tetragonal phase, I >>am getting negative ionic phase leading to? negative polarization for Pb. >>? ? ? ? ? ? ? ? If I compare the out put file for both cubic and? >>tertragonal phase, to my surprise in the cubic phase the total ionic? phase >>comes out to be positive (actually, if you sum it is? negative), where as in >>the case of tetragonal phase the ionic phase? comes out to be negative (but, >>it is positive if you sum the same? way as for the cubic). >>? ? ? ? ? ? ? ? I do not understand this differrent summing rule for? >>different phases. I am attaching both the input and out files for? cubic and >>tetragonal phases. I would appreciate any useful? suggestions to clear this >>point. >>I am very sorry for the long mail and data files. >> >>- 620015 >>India >> >>_______________________________________________ >>Pw_forum mailing list >>Pw_forum at pwscf.org >>http://www.democritos.it/mailman/listinfo/pw_forum > >--- >Stefano Baroni - SISSA? &? DEMOCRITOS National Simulation Center -? Trieste >http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) /? >stefanobaroni (skype) > >La morale est une logique de l'action comme la logique est une morale? de la >pens?e - Jean Piaget > >Please, if possible, don't? send me MS Word or PowerPoint attachments >Why? See:? http://www.gnu.org/philosophy/no-word-attachments.html > > > > > > _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum ---Stefano Baroni - SISSA??&??DEMOCRITOS National Simulation Center - Triestehttp://www.sissa.it/~baroni /?[+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) La morale est une logique de l'action comme la logique est une morale de la pens?e - Jean Piaget Please, if possible, don't??send me MS Word or PowerPoint attachmentsWhy? See:??http://www.gnu.org/philosophy/no-word-attachments.html _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20080709/25151a04/attachment.htm
