[Pw_forum] Could not find the mode symmetry after phonon frequency calculation of gamma point

[Sitangshu Bhattacharya]

Dear Dr. Paolo,

Just to check, these are the two results done on a same structure (ibrav 4)
and level of convergence but with different pseudos..... One with PW91 and
the other with PBE. PW91 seems to offer correct results on mode symmetry
analysis. The optical frequency values are however close...

[image: Inline image 1]

[image: Inline image 2]
Regards,

Sitangshu




On Mon, Jan 8, 2018 at 1:15 PM, Paolo Giannozzi <p.giannozzi at gmail.com>
wrote:

> Pseudopotentials do not affect symmetry. I would try to reduce the
> convergence threshold for both the scf and the phonon calculation
>
> On Mon, Jan 8, 2018 at 5:16 AM, Sitangshu Bhattacharya <
> sitangshu at iiita.ac.in> wrote:
>
>> Dear Zhishuo,
>>
>> Check your scf report file. This same mode symmetry should be mentioned
>> there. If it is there, replace with a proper pseudo. These things comes
>> when pseudos are not well tested at the initial level.
>>
>> Regards,
>> Sitangshu
>>
>> On Sun, Jan 7, 2018 at 9:59 PM, 黄志硕 <zhishuohuang at gmail.com> wrote:
>>
>>> Dear Quantum Espresso users,
>>>
>>>
>>>
>>> I just finished the phonon calculation at Gamma point of a material with
>>> T_h symmetry. But it seems that the code could not determine the mode
>>> symmetry as shown in the output file:
>>>
>>>
>>>
>>> ###############################################################
>>>
>>>      Mode symmetry, T_h (m-3)   point group:
>>>
>>>
>>>
>>>      freq (  1 -  3) =          9.1  [cm-1]   --> T_u             I
>>>
>>>      freq (  4 -  6) =         14.5  [cm-1]   --> T_u             I
>>>
>>>      freq (  7 -  9) =         48.9  [cm-1]   --> T_g             R
>>>
>>>      freq ( 10 - 12) =         81.9  [cm-1]   --> T_g             R
>>>
>>>      freq ( 13 - 15) =        100.1  [cm-1]   --> T_u             I
>>>
>>>      freq ( 16 - 16) =        254.2  [cm-1]   -->   ?
>>>
>>>      freq ( 17 - 17) =        254.2  [cm-1]   -->   ?
>>>
>>>      freq ( 18 - 20) =        265.1  [cm-1]   --> T_g             R
>>>
>>>      freq ( 21 - 23) =        347.7  [cm-1]   --> T_u             I
>>>
>>>      freq ( 24 - 26) =        349.8  [cm-1]   --> T_u             I
>>>
>>>      freq ( 27 - 27) =        350.5  [cm-1]   --> A_u
>>>
>>>      freq ( 28 - 28) =        394.8  [cm-1]   -->   ?
>>>
>>>      freq ( 29 - 29) =        394.8  [cm-1]   -->   ?
>>>
>>>      freq ( 30 - 32) =        395.2  [cm-1]   --> T_u             I
>>>
>>>      freq ( 33 - 35) =        396.8  [cm-1]   --> T_g             R
>>>
>>>      freq ( 36 - 36) =        398.8  [cm-1]   -->   ?
>>>
>>>      freq ( 37 - 37) =        398.8  [cm-1]   -->   ?
>>>
>>>      freq ( 38 - 40) =        479.4  [cm-1]   --> T_g             R
>>>
>>> …….
>>>
>>> …….
>>>
>>> ###############################################################
>>>
>>>
>>>
>>> As from above, the code could notice the point group is T_h. However,
>>> for the two-fold modes (16 and 17, 28 and 29, 36 and 37, actually, all the
>>> two-fold modes have the same problem), which seem to be E_g (or E_u) mode,
>>> there is no symmetry information. In stead, there is only two “?” marks.
>>>
>>>
>>>
>>> Any hint for this problem could be very welcome.
>>>
>>>
>>>
>>> Best regards
>>>
>>> Zhishuo Huang
>>>
>>>
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> http://pwscf.org/mailman/listinfo/pw_forum
>>>
>>
>>
>>
>> --
>> **********************************************
>> Sitangshu Bhattacharya (সিতাংশু ভট্টাচার্য), Ph.D
>> Assistant Professor,
>> Room No. 2221, CC-1,
>> Nanoscale Electro-Thermal Laboratory,
>> Department of Electrical and Communication Engineering,
>> Indian Institute of Information Technology-Allahabad
>> Uttar Pradesh 211 012
>> India
>> Telephone: 91-532-2922000 Extn.: 2131
>> Web-page: http://profile.iiita.ac.in/sitangshu/
>> Institute: http://www.iiita.ac.in/
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://pwscf.org/mailman/listinfo/pw_forum
>>
>
>
>
> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>
> _______________________________________________
> Pw_forum mailing list
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> http://pwscf.org/mailman/listinfo/pw_forum
>



-- 
**********************************************
Sitangshu Bhattacharya (সিতাংশু ভট্টাচার্য), Ph.D
Assistant Professor,
Room No. 2221, CC-1,
Nanoscale Electro-Thermal Laboratory,
Department of Electrical and Communication Engineering,
Indian Institute of Information Technology-Allahabad
Uttar Pradesh 211 012
India
Telephone: 91-532-2922000 Extn.: 2131
Web-page: http://profile.iiita.ac.in/sitangshu/
Institute: http://www.iiita.ac.in/
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