Re: [Wien] Spontaneous polarization of PbTiO3

[Rubel, Oleg]

Dear Gavin, 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. Thank you  Oleg  On May 8, 2018, at 04:05, Gavin Abo <gs...@crimson.ua.edu> wrote: In the BaTiO3 tutorial, lambda1.struct and lambda0.struct both have spacegroup 99_P4mm and 8 symmetry operations [ https://github.com/spichardo/BerryPI/wiki/Tutorial-1:-Spontaneous-Polarization-in-BaTiO3 ]. I see a sentence in the tutorial: The symmetry operations are identical (!) to the lambda1 case, in spite of a higher symmetry of the lambda0 structure. Perhaps that is the sentence that another user got that the symmetry might need to remain the same [ https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg16112.html ]. The tet1.struct has spacegroup 99_P4mm, while cubic.struct has spacegroup 221_Pm3m. According to the tutorial: 8. Spontaneous polarization is obtained by taking a difference in polarization between P(lambda1) and P(lambda0) -> Difference between tet1 and cubic for the PbTiO3 case? 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? On 5/7/2018 4:36 AM, Lokanath Patra wrote: Dear Oleg, 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. Best regards Lokanath On Wed, May 2, 2018 at 7:25 PM, Oleg Rubel <rub...@mcmaster.ca> wrote: Dear Lokanath, PbTiO3 was one of compounds used in the test of BerryPI (see Table 3 in http://olegrubel.mcmaster.ca/publications/2013/Ahmed_CPC_184_2013.pdf). 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. I hope it will help Oleg -- Oleg Rubel (PhD, PEng) Department of Materials Science and Engineering McMaster University JHE 359, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada Email: rub...@mcmaster.ca Tel: +1-905-525-9140, ext. 24094 Web: http://olegrubel.mcmaster.ca On 2018-May-02 08:38, Lokanath Patra wrote: Dear all, 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. Regards Lokanath -- Lokanath Patra Ph.D Scholar Dept. of Physics School of Applied and Basic Sciences Central University of Tamil Nadu Thiruvarur Tamil Nadu - 610004 Ph no - +91-8675834507 ------------------------------------------------------------------------ Central University of Tamil Nadu is in not responsible for the contents of this email. The sender takes responsibility for the content of this email. /This mail is also governed by the relevant disclaimer policies of Central University of Tamil Nadu. <http://cutn.ac.in/disclaimer.php>/ _______________________________________________ Wien mailing list w...@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at:  http://www.mail-archive.com/wie...@zeus.theochem.tuwien.ac.at/index.html _______________________________________________ Wien mailing list w...@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at:  http://www.mail-archive.com/wie...@zeus.theochem.tuwien.ac.at/index.html -- Lokanath Patra Ph.D Scholar Dept. of Physics School of Applied and Basic Sciences Central University of Tamil Nadu Thiruvarur Tamil Nadu - 610004 Ph no - +91-8675834507 Central University of Tamil Nadu is in not responsible for the contents of this email. The sender takes responsibility for the content of this email. This mail is also governed by the relevant disclaimer policies of Central University of Tamil Nadu. _______________________________________________ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at:  http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html

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