[Wien] Spontaneous polarization of PbTiO3

Thu May 10 08:49:28 CEST 2018

 Dear Gavin,

Now I have used the same tetragonal structure with centrosymmetric atomic
positions.  The polarization calculated with the centrosymmetric structure
is in an order of e-13. So it didn't modify the results significantly. I am
attaching the currently used centrosymmetric, non-centrosymmetric
structures.

Regards
Lokanath

On Tue, May 8, 2018 at 2:08 PM, Lokanath Patra <lokanath at students.cutn.ac.in
> wrote:

> Dear Gavin,
>
> Now I have used the same tetragonal structure with centrosymmetric atomic
> positions. I am attaching the file. The polarization calculated with the
> centrosymmetric structure is in an order of e-13. So it didn't modify the
> results significantly. I am attaching the currently used centrosymmetric,
> non-centrosymmetric structures as well as the screen shots of the results.
>
> Regards
> Lokanath
>
> On Tue, May 8, 2018 at 9:20 AM, Rubel, Oleg <rubelo at mcmaster.ca> wrote:
>
>> 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 <gsabo at 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:-Sponta
>> neous-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/w
>> ien at 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> 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
>>> <https://maps.google.com/?q=359,+1280+Main+Street+West,+Hamilton,+Ontario+L8S+4L8,+Canada&entry=gmail&source=g>
>>> Email: 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
>>
>> ------------------------------
>>
>> 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>*
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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
>

-- 
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 
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