<table cellspacing='0' cellpadding='0' border='0' ><tr><td valign='top' style='font: inherit;'>Hi,<br><br>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. <br><br>Besides, use lower convergence threshold, conv_thr=1d-8, 1e-6 looks quite high.<br><br>Bests,<br>Eyvaz.<br><br>-------------------------------------------------------------------<br>
Prof. Eyvaz Isaev, <br>
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, <br>
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden <br>
Condensed Matter Theory Group, Uppsala University, Sweden <br>
Eyvaz.Isaev@fysik.uu.se, isaev@ifm.liu.se, eyvaz_isaev@yahoo.com<br><br>--- On <b>Wed, 7/9/08, Stefano Baroni <i><baroni@sissa.it></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;">From: Stefano Baroni <baroni@sissa.it><br>Subject: Re: [Pw_forum] negative value of polarization and Z* for Pb in Tetragonal PbTiO3 and discrepancy<br>To: "sathya subramanyan" <sathya_sheela1985001@rediffmail.com>, "PWSCF Forum" <pw_forum@pwscf.org><br>Date: Wednesday, July 9, 2008, 3:53 AM<br><br><div id="yiv1925734647">what I was suggesting is that YOU perform a convergence test and ley us know ...<div>SB</div><div><br><div><div>On Jul 8, 2008, at 6:44 PM, sathya subramanyan wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><p> Dear Sir,<br> 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.:<br> <br> THE I/P FILE FOR TETRAGONAL PbTiO3<br> <br> &CONTROL<br> calculation = 'nscf'<br> pseudo_dir = '/home/nbaski/espresso-4.0/pseudo/'<br> outdir = '/home/nbaski/tmp/'<br> lberry = .true.<br> gdir = 3<br> nppstr = 7<br> /<br> &SYSTEM<br> ibrav = 6<br> celldm(1) = 7.3415<br> celldm(3) = 1.0653<br> nat = 5<br> ntyp = 3<br> nbnd =
22<br> ecutwfc = 30.0<br> occupations = 'fixed'<br> degauss = 0.00<br> /<br> &ELECTRONS<br> conv_thr = 1e-5<br> mixing_beta = 0.3<br> /<br> ATOMIC_SPECIES<br> Pb 207.2 Pb.vdb.UPF<br> Ti 47.867 Ti.vdb.UPF<br> O 15.9994 O.vdb.UPF<br> ATOMIC_POSITIONS<br> Pb 0.00000 0.00000 0.01000<br> Ti 0.50000 0.50000 0.53770<br> O 0.50000 0.50000 0.11180<br> O 0.00000 0.50000 0.61740<br> O 0.50000 0.00000 0.61740<br> K_POINTS {automatic}<br> 4 4 7 1 1 1<br> <br> <br> <br> <br> <br> Thank
you in advance for any help<br> SATHYA SHEELA.S<br> Grad. Student<br> Department of Physics<br> National Institute of Technology<br> Tiruchirapalli <br> <br> <br> On Fri, 27 Jun 2008 Stefano Baroni wrote :<br> >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<br> ><br> >On Jun 27, 2008, at 11:51 AM, sathya subramanyan wrote:<br> ><br> >><br> >>Dear Developers,<br> >>
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.<br> >><br> >> 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.<br> >> 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).<br> >> 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.<br> >>I am very sorry for the long mail and data files.<br> >><br> >>- 620015<br> >>India<br> >><br> >>_______________________________________________<br> >>Pw_forum mailing list<br> >><a rel="nofollow" target="_blank" href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br> >><a rel="nofollow" target="_blank" href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</a><br> ><br> >---<br> >Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste<br> ><a rel="nofollow"
target="_blank" href="http://www.sissa.it/%7Ebaroni">http://www.sissa.it/~baroni</a> / [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)<br> ><br> >La morale est une logique de l'action comme la logique est une morale de la pensée - Jean Piaget<br> ><br> >Please, if possible, don't send me MS Word or PowerPoint attachments<br> >Why? See: <a rel="nofollow" target="_blank" href="http://www.gnu.org/philosophy/no-word-attachments.html">http://www.gnu.org/philosophy/no-word-attachments.html</a><br> ><br> ><br> ><br> ><br> ><br> ><br> </p> <br><br> <table style="font-family: Verdana; font-size: 11px; line-height: 15px;" border="0" cellpadding="0" cellspacing="0" height="57" width="644"><tbody><tr><td><a rel="nofollow" target="_blank"
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class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px;"><div style=""><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px;"><div style=""><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px;
text-transform: none; white-space: normal; widows: 2; word-spacing: 0px;"><div style=""><div><div style="margin: 0px;"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">---</span></font></div><div style="margin: 0px;"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Stefano Baroni - SISSA</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"> </span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">&</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"> </span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">DEMOCRITOS National Simulation Center - Trieste</span></font></div><div style="margin: 0px;"><font
class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><a rel="nofollow" target="_blank" href="http://www.sissa.it/%7Ebaroni">http://www.sissa.it/~baroni</a> / [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)</span></font></div><div style="margin: 0px; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal; font-size-adjust: none; font-stretch: normal; -x-system-font: none; min-height: 14px; font-size: 12px;"><br style="font-size: 12px;"></div><div style="margin: 0px; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal; font-size-adjust: none; font-stretch: normal; -x-system-font: none; min-height: 14px; font-size: 12px;"><span class="Apple-style-span" style="font-size: 14px;"><div style="margin: 0px;"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size:
12px;">La morale est une logique de l'action comme la logique est une morale de la pensée - Jean Piaget</span></font></div><div style="margin: 0px;"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"><br></span></font></div></span></div><div style="margin: 0px;"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Please, if possible, don't</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;"> </span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">send me MS Word or PowerPoint attachments</span></font></div><div style="margin: 0px;"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px;">Why? See:</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size:
12px;"> </span></font><font class="Apple-style-span" size="3" color="#0023e9"><span class="Apple-style-span" style="font-size: 12px;"><a rel="nofollow" target="_blank" href="http://www.gnu.org/philosophy/no-word-attachments.html">http://www.gnu.org/philosophy/no-word-attachments.html</a></span></font></div><div><font class="Apple-style-span" size="3" color="#0023e9"><span class="Apple-style-span" style="font-size: 12px;"><br class="webkit-block-placeholder"></span></font></div></div></div></span><br class="Apple-interchange-newline"></div></span><br class="Apple-interchange-newline"></div></span><br class="Apple-interchange-newline"></div></span><br class="Apple-interchange-newline"> </div><br></div></div><pre>_______________________________________________<br>Pw_forum mailing list<br>Pw_forum@pwscf.org<br>http://www.democritos.it/mailman/listinfo/pw_forum</pre></blockquote></td></tr></table><br>