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<div>Dear Gavin,</div>
<div><br>
</div>
<div>This is a very good point. I certainly agree that the symmetry of the cubic structure should be reduced to that of the tetragonal structure.</div>
<div><br>
</div>
<div>Thank you </div>
<div>Oleg </div>
<div><br>
On May 8, 2018, at 04:05, Gavin Abo <<a href="mailto:gsabo@crimson.ua.edu">gsabo@crimson.ua.edu</a>> wrote:<br>
<br>
</div>
<blockquote type="cite">
<div>
<p><font face="Times New Roman">In the BaTiO3 tutorial, lambda1.struct and lambda0.struct both have spacegroup 99_P4mm and 8 symmetry operations [
<a class="moz-txt-link-freetext" href="https://github.com/spichardo/BerryPI/wiki/Tutorial-1:-Spontaneous-Polarization-in-BaTiO3">
https://github.com/spichardo/BerryPI/wiki/Tutorial-1:-Spontaneous-Polarization-in-BaTiO3</a> ].</font></p>
<p><font face="Times New Roman">I see a sentence in the tutorial:<br>
</font></p>
<p><font face="Times New Roman"><i>The symmetry operations are identical (!) to the lambda1 case, in spite of a higher symmetry of the lambda0 structure.</i><br>
</font></p>
<p>Perhaps that is the sentence that another user got that the symmetry might need to remain the same [
<a class="moz-txt-link-freetext" href="https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg16112.html">
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg16112.html</a> ].<br>
</p>
<p>The tet1.struct has spacegroup 99_P4mm, while cubic.struct has spacegroup 221_Pm3m.</p>
<p>According to the tutorial:<br>
</p>
<p><i>8. Spontaneous polarization is obtained by taking a difference in polarization between P(lambda1) and P(lambda0)</i> -> Difference between tet1 and cubic for the PbTiO3 case?<br>
</p>
<p>For PbTiO3, is it okay that there are "8 NUMBER OF SYMMETRY OPERATIONS" in cubic.struct and "48 NUMBER OF SYMMETRY OPERATIONS" in tet1.struct for the spontaneous polarization calculation?<br>
</p>
<div class="moz-cite-prefix">On 5/7/2018 4:36 AM, Lokanath Patra wrote:<br>
</div>
<blockquote type="cite" cite="mid:CAEoKfGie3Q7pg+X-f=O=gMK_Tgdedbbo0jkAN_1JUbybvV1_TA@mail.gmail.com">
<div dir="ltr">Dear Oleg,
<div><br>
</div>
<div>I am attaching the structure files which I have used for the calculation. I have used similar procedure as given for BaTiO3 tutorial (same parameters for initialising and same k-point mesh for Berrypi. The calculated polarisation for cubic phase is very
low. So so spontaneous polarisation is still very low as given in my previous mail. I am unable to trace my mistakes.</div>
<div><br>
</div>
<div>Best regards</div>
<div>Lokanath</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Wed, May 2, 2018 at 7:25 PM, Oleg Rubel <span dir="ltr">
<<a href="mailto:rubelo@mcmaster.ca" target="_blank" moz-do-not-send="true">rubelo@mcmaster.ca</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<span class="">Dear Lokanath,<br>
<br>
PbTiO3 was one of compounds used in the test of BerryPI (see Table 3 in<br>
<a href="http://olegrubel.mcmaster.ca/publications/2013/Ahmed_CPC_184_2013.pdf" rel="noreferrer" target="_blank" moz-do-not-send="true">http://olegrubel.mcmaster.ca/p<wbr>ublications/2013/Ahmed_CPC_184<wbr>_2013.pdf</a>). I think you should also compute polarization
in the cubic structure of PbTiO3 even though they are deemed to have no polarization. If this does not help, I would suggest looking into the structure more carefully, tetragonal distortion, compare with experiment, etc.<br>
<br>
<br>
I hope it will help<br>
Oleg<br>
<br>
-- <br>
Oleg Rubel (PhD, PEng)<br>
Department of Materials Science and Engineering<br>
McMaster University<br>
JHE <a href="https://maps.google.com/?q=359,+1280+Main+Street+West,+Hamilton,+Ontario+L8S+4L8,+Canada&entry=gmail&source=g" moz-do-not-send="true">
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http://olegrubel.mcmaster.ca</a><br>
<br>
On 2018-May-02 08:38, Lokanath Patra wrote:<br>
</span>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
<div class="h5">Dear all,<br>
<br>
I am using Berry phase tutorial to calculate the polarization of PbTiO3. I have followed the BaTiO3 tutorial. I have two structures, one is tetragonal (non-centrosymmetric) and the second one is cubic (centrosymmetric). I have calculated the (spontaneous) polarization
as 1.189769e-01 C/m2 (as the cubic system doesn't posses any polarization) which is very low as the reported values are around 80 to 100 µC/cm2. Please help me.<br>
<br>
Regards<br>
Lokanath<br>
<br>
-- <br>
Lokanath Patra<br>
Ph.D Scholar<br>
Dept. of Physics<br>
School of Applied and Basic Sciences<br>
Central University of Tamil Nadu<br>
Thiruvarur<br>
Tamil Nadu - 610004<br>
Ph no - +91-8675834507<br>
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-- <br>
<div class="gmail_signature" data-smartmail="gmail_signature">
<div dir="ltr"><span style="color:rgb(136,136,136)">Lokanath Patra</span>
<div style="color:rgb(136,136,136)">Ph.D Scholar</div>
<div style="color:rgb(136,136,136)">Dept. of Physics</div>
<div style="color:rgb(136,136,136)">School of Applied and Basic Sciences</div>
<div style="color:rgb(136,136,136)">Central University of Tamil Nadu</div>
<div style="color:rgb(136,136,136)">Thiruvarur</div>
<div style="color:rgb(136,136,136)">Tamil Nadu - 610004</div>
<div style="color:rgb(136,136,136)">Ph no - +91-8675834507</div>
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