[Wien] Spontaneous polarization of PbTiO3

[Gavin Abo]

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 <rubelo at mcmaster.ca 
> <mailto:rubelo at 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
>     <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
>     <https://maps.google.com/?q=359,+1280+Main+Street+West,+Hamilton,+Ontario+L8S+4L8,+Canada&entry=gmail&source=g>
>     Email: rubelo at mcmaster.ca <mailto:rubelo at 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
>
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>
> -- 
> 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
>
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